Reading mechanism for dosimeter

ABSTRACT

Described is a method comprising the following steps: (a) moving a selected optically stimulated luminescence (OSL) sensor of two or OSL sensors mounted on a dosimeter sled to a reading position for an OSL reader; (b) reading the selected OSL sensor at the reading position using the OSL reader to measure a radiation dosage to which a dosimeter in which the dosimeter sled has been mounted has been exposed; and (c) repeating steps (a) and (b) for each of the two or more OSL sensors, wherein each OSL sensor comprises an optically stimulated luminescent material (OSLM) mounted in one or more cylindrical cup-shaped energy compensating filters, and wherein the dosimeter sled is part of a dosimeter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority to U.S. Provisional PatentApplication No. 61/294,142 to Yoder, entitled RADIATION DOSIMETER ANDRADIATION READER, filed Jan. 12, 2010, which is incorporated herein byreference in its entirety. This application also makes reference to thefollowing U.S. patent applications: U.S. patent application Ser. No.______ filed ______, entitled PORTABLE DOSIMETER; U.S. patentapplication Ser. No. ______ filed ______, entitled NOVEL FILTERS FOR USEIN DOSIMETRY; U.S. patent application Ser. No. ______ filed ______,entitled DOSIMETER SLED; U.S. patent application Ser. No. ______ filed______, entitled PORTABLE READER FOR A DOSIMETER; U.S. patentapplication Ser. No. ______ filed ______, entitled DATA STORAGEMECHANISM AND COMMUNICATION MECHANISM FOR PORTABLE DOSIMETER; U.S.patent application Ser. No. ______ filed ______, entitled READINGMECHANISM FOR DOSIMETER; U.S. patent application Ser. No. ______ filed______, entitled POWER SYSTEM FOR DOSIMETER READER; U.S. patentapplication Ser. No. ______ filed ______, entitled OPTICAL SYSTEM FORDOSIMETER READER; U.S. patent application Ser. No. ______ filed ______,entitled DOSIMETER WITH RFID TAG; and U.S. patent application Ser. No.______ filed ______, entitled NOVEL RFID TAG FOR USE IN DOSIMETRY.

BACKGROUND

1. Field of the Invention

The present invention relates to a method for reading a radiationdosimeter.

2. Related Art

Existing methods for reading dosimeters make it difficult to readdosimeters in the field.

SUMMARY

According to a first broad aspect, the present invention provides amethod comprising the following steps: (a) moving a selected opticallystimulated luminescence (OSL) sensor of two or more OSL sensors mountedon a dosimeter sled to a reading position for the selected OSL sensor;(b) reading the selected OSL sensor at the reading position using an OSLreader to measure a radiation dosage to which a dosimeter in which thedosimeter sled has been mounted has been exposed; and (c) repeatingsteps (a) and (b) for each of the two or more OSL sensors, wherein eachOSL sensor comprises an optically stimulated luminescent material (OSLM)mounted in one or more cylindrical cup-shaped energy compensatingfilters, and wherein the dosimeter sled is part of a dosimeter.

According to a second broad aspect, the present invention provides amethod comprising the following steps: (a) moving an opticallystimulated luminescence (OSL) sensor mounted on a dosimeter sled to areading position for an OSL reader; and (b)reading the OSL sensor at thereading position using the OSL reader to measure a radiation dosage towhich a dosimeter in which the dosimeter sled has been mounted has beenexposed, wherein the OSL sensor comprises an optically stimulatedluminescent material (OSLM) mounted in one or more cylindricalcup-shaped energy compensating filters.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate exemplary embodiments of theinvention, and, together with the general description given above andthe detailed description given below, serve to explain the features ofthe invention.

FIG. 1 is an image of the bottom of a radiation dosimeter according toone embodiment of the present invention;

FIG. 2 is an image of the top of the radiation dosimeter of FIG. 1 andof the top of the upper housing of the radiation dosimeter of FIG. 1;

FIG. 3 is an image of the bottom of the upper housing of FIG. 2;

FIG. 4 is an image of the top of the lower housing of the radiationdosimeter of FIG. 1;

FIG. 5 is an image of the bottom of the lower housing of FIG. 4;

FIG. 6 is an image of the top of the sled of the radiation dosimeter ofFIG. 1;

FIG. 7 is an image of the bottom of the sled of FIG. 6;

FIG. 8 is an image of the reference OSL sensor the sled of FIG. 6showing the reference OSL sensor in a disassembled state;

FIG. 9 is an image of the reference OSL sensor of FIG. 6 in an assembledstate;

FIG. 10 is an image of the sled of FIG. 6 being slid into the lowerhousing of FIG. 4;

FIG. 11 is an image of the dosimeter sled of FIG. 6 fully slid into thelower housing of FIG. 4;

FIG. 12 is a top perspective view of an upper housing of a radiationdosimeter according to one embodiment of the present invention;

FIG. 13 is a bottom perspective view of the upper housing of FIG. 12;

FIG. 14 is a top plan view of the upper housing of FIG. 12;

FIG. 15 is a bottom plan view of the upper housing of FIG. 12;

FIG. 16 is a cross-sectional view of the upper housing of FIG. 12 takenalong line A-A of FIG. 14;

FIG. 17 is a top perspective view of a lower housing of a radiationdosimeter according to one embodiment of the present invention;

FIG. 18 is a bottom perspective view of the lower housing of FIG. 17;

FIG. 19 is a top plan view of the lower housing of FIG. 17;

FIG. 20 is a bottom plan view of the lower housing of FIG. 17;

FIG. 21 is a cross-sectional view of the lower housing of FIG. 17 takenalong line B-B of FIG. 19;

FIG. 22 is a cross-sectional view of the lower housing of FIG. 17 takenalong line C-C of FIG. 20;

FIG. 23 is a cross-sectional view of the lower housing of FIG. 17 takenalong line D-D of FIG. 21;

FIG. 24 is a cross-sectional view of the lower housing of FIG. 17 takenalong line E-E of FIG. 22;

FIG. 25 is a top perspective view of a dosimeter sled body of adosimeter according to one embodiment of the present invention;

FIG. 26 is a bottom perspective view of the dosimeter sled body of FIG.25;

FIG. 27 is a top plan view of the dosimeter sled body of FIG. 25;

FIG. 28 is a bottom plan view of the dosimeter sled body of FIG. 25;

FIG. 29 is a side view of the dosimeter sled body of FIG. 25;

FIG. 30 is a cross-sectional view of the dosimeter sled body of FIG. 25taken along line E-E of FIG. 27;

FIG. 31 is an end view of the dosimeter sled body of FIG. 25;

FIG. 32 is an end view of the dosimeter sled body of FIG. 25 of theopposite end of the dosimeter sled from the end shown in FIG. 31;

FIG. 33 is a cross-sectional view of the dosimeter sled body of FIG. 25taken along line F-F of FIG. 28;

FIG. 34 is bottom plan view of a dosimeter sled according to oneembodiment of the present invention;

FIG. 35 is a cross-sectional view of the dosimeter sled of FIG. 34 takenalong line G-G of FIG. 34.

FIG. 36 is a top perspective view of an upper housing of a radiationdosimeter according to one embodiment of the present invention;

FIG. 37 is a top perspective view of an upper housing of a radiationdosimeter according to one embodiment of the present invention;

FIG. 38 is an exploded view of a radiation dosimeter according to oneembodiment of the present invention;

FIG. 39 is a bottom plan view of the dosimeter sled body of theradiation dosimeter of FIG. 38;

FIG. 40 is an image of the dosimeter sled of the radiation dosimeter ofFIG. 38;

FIG. 41 is a top perspective view of an upper housing of a radiationdosimeter according to one embodiment of the present invention;

FIG. 42 is a bottom perspective view of the upper housing of FIG. 41;

FIG. 43 is a top plan view of the upper housing of FIG. 41;

FIG. 44 is a bottom plan view of the upper housing of FIG. 41;

FIG. 45 is a cross-sectional view taken along line H-H of FIG. 43;

FIG. 46 is a top perspective view of a dosimeter sled body of adosimeter according to one embodiment of the present invention;

FIG. 47 is a bottom perspective view of the dosimeter sled body of FIG.46;

FIG. 48 is a top plan view of the dosimeter sled body of FIG. 46;

FIG. 49 is a bottom plan view of the dosimeter sled body of FIG. 46;

FIG. 50 is a side view of the dosimeter sled body of FIG. 46;

FIG. 51 is a cross-sectional view of the dosimeter sled body of FIG. 46taken along line I-I of FIG. 48;

FIG. 52 is an end view of the dosimeter sled body of FIG. 46;

FIG. 53 is an end view of the dosimeter sled body of FIG. 46 of theopposite end of the dosimeter sled from the end shown in FIG. 51;

FIG. 54 is a cross-sectional view of the dosimeter sled body of FIG. 46taken along line J-J of FIG. 49;

FIG. 55 is a close-up perspective view of the FNTD holder of thedosimeter sled body of FIG. 46;

FIG. 56 is a cross-sectional view of a lower housing of a dosimeter, theupper housing of FIG. 41 and the dosimeter sled body of FIG. 46assembled together;

FIG. 57 is a cross-sectional view of a sealing engagement between thelower housing and upper housing of FIG. 56;

FIG. 58 is a top plan view of an OSL sensor according to one embodimentof the present invention;

FIG. 59 is a cross-sectional view of the OSL sensor of FIG. 58 takenalong line K-K:

FIG. 60 is a top plan view of an inner filter in which is mounted anOSLM of the OSL sensor of FIG. 58;

FIG. 61 is a cross-sectional view of an inner filter and OSLM of FIG. 60taken along line L-L of FIG. 60:

FIG. 62 is a top plan view of a retaining ring of the OSL sensor of FIG.58 with the retaining ring shown in a relaxed state;

FIG. 63 is a cross-sectional view of the retaining ring of FIG. 58 takenalong line M-M of FIG. 62:

FIG. 64 is a top plan view of a cylindrical cup-shaped outer filter ofthe OSL sensor of FIG. 58;

FIG. 65 is a cross-sectional view of the outer filter of FIG. 61 takenalong line N-N of FIG. 64:

FIG. 66 is an image of a radiation dosimeter of the present inventionwith a wristband according to one embodiment of the present inventionwith the wristband threaded below the lower housing of the radiationdosimeter;

FIG. 67 is an image of a radiation dosimeter of the present inventionwith a wristband according to one embodiment of the present inventionwith the wristband threaded above the upper housing of the radiationdosimeter;

FIG. 68 is an image of a radiation dosimeter of the present inventionwith a clip according to one embodiment of the present invention;

FIG. 69 is an image of a dosimeter reader according to one embodiment ofthe present invention;

FIG. 70 is a close-up image of a dosimeter reader body of the dosimeterreader of FIG. 69;

FIG. 71 is an image of a dosimeter reader case and the dosimeter readerbody of the dosimeter reader of FIG. 69;

FIG. 72 is an image of a dosimeter drawer of the dosimeter reader ofFIG. 69;

FIG. 73 is a close-up image of one of two loop retainers extendingthrough a drawer base of the dosimeter drawer of FIG. 72;

FIG. 74 is a close-up image of the other loop retainer extending througha drawer base of the dosimeter drawer of FIG. 72;

FIG. 75 shows two spring tabs extending through openings in the drawerbase of the dosimeter drawer of FIG. 72;

FIG. 76 is an image of the dosimeter reader of FIG. 69 with a housingcover removed to provide a close-up image of the RFID tag reader of thedosimeter reader of FIG. 69;

FIG. 77 image of the dosimeter reader body of the dosimeter reader ofFIG. 69 with the housing cover removed to show details of a ready regionhousing, a reader housing and an OSL reader of the dosimeter reader ofFIG. 69;

FIG. 78 is an image showing a sled slider of the OSL reader of FIG. 77;

FIG. 79 is an image showing a sled slider motor of the OSL reader ofFIG. 77 and a wall of the reader housing;

FIG. 80 is an image of the OSL reader of FIG. 77 with the sliderpositioned so that the optical light pipe of the OSL reader may be seen;

FIG. 81 is a close-up image of the optical light-pipe of FIG. 80;

FIG. 82 is a schematic drawing that shows how a dosimeter sled blocksthe light path of a photo-optic sensor according to one embodiment ofthe present invention when the dosimeter sled is not in a readingposition for an OSL sensor;

FIG. 83 is a schematic drawing that shows how a notch in the dosimetersled opens the light path of the photo-optic sensor of FIG. 82 when thedosimeter sled in a reading position for an OSL sensor;

FIG. 84 is an image of the underside of the dosimeter reader body of thedosimeter reader of FIG. 69;

FIG. 85 is an image of the underside of the OSL reader of FIG. 77;

FIG. 86 is an image of the loop retainer elevator of an elevatorcarriage of the dosimeter reader body of FIG. 84 in a fully loweredposition;

FIG. 87 is an image of the loop retainer elevator of FIG. 87 in anintermediate raised position;

FIG. 88 is an image of the loop retainer elevator of FIG. 87 in a fullyraised position;

FIG. 89 is an image of the elevator carriage of the dosimeter readerbody of FIG. 84;

FIG. 90 is an image showing a pinion gear of the elevator carriage andtwo retaining tabs slidably mounted in curved slots in the pinion gear;

FIG. 91 is a close up image of the pinion gear and retaining tabs ofFIG. 89;

FIG. 92 is an image of the photo-optical engine frame of the dosimeterreader of FIG. 69;

FIG. 93 is an image of the photo-optical engine frame of FIG. 92 from adifferent angle;

FIG. 94 is an exploded view of a photo-optical engine of the OSL readerof the dosimeter reader of FIG. 69;

FIG. 95 is a partially exploded view of the photo-optical engine of FIG.94 with the filter optical assembly shown in simplified form in anassembled state and the sides of the body of the photo-optical enginemade transparent to better show interior detail;

FIG. 96 is a perspective view of the photo-optical engine of FIG. 94 ina partially assembled state with various features of the photo-opticalengine made transparent to better show interior detail;

FIG. 97 is a side view of the partially assembled photo-optical engineof FIG. 96 with various features of the photo-optical engine madetransparent to better show interior detail;

FIG. 98 is a perspective view of an LED interconnect PCB assembly of thephoto-optical engine of FIG. 94;

FIG. 99 is an exploded view of the LED interconnect PCB assembly of FIG.98 with the PCB of the LED interconnect PCB assembly shown in asimplified form;

FIG. 100 is a side view of the photo-optical engine of FIG. 94 in anassembled state with part of the photo-optical engine broken away toshow interior details;

FIG. 101 is a cross-sectional view of the circled region of thephoto-optical engine in FIG. 99.

FIG. 102 is a schematic diagram of the OSL reader and RFID tag reader ofthe dosimeter reader of FIG. 69;

FIG. 103 is an image of a radiation dosimeter of the present inventionloaded in the dosimeter drawer of the dosimeter reader of FIG. 69 withthe radiation dosimeter in a starting position;

FIG. 104 is a close-up image of the radiation dosimeter and dosimeterdrawer of FIG. 103;

FIG. 105 is an image showing the radiation dosimeter of FIG. 103 rotatedto a rotated position where the upper housing of the radiation dosimeteris released from the lower housing of the radiation dosimeter;

FIG. 106 is a cross-sectional view of a portion of the lower housing ofthe radiation dosimeter of FIG. 103 and the two spring tabs of thedosimeter reader of FIG. 69 showing how the two spring tabs of thedosimeter reader retain the lower housing of the radiation dosimeter onthe drawer base of the dosimeter drawer of FIG. 103 as dosimeter drawerand radiation dosimeter are pushed towards a dosimeter ready region ofthe dosimeter reader;

FIGS. 107, 108 and 109 are images showing the radiation dosimeter anddosimeter drawer of FIG. 103 being pushed into the ready region housingof the dosimeter reader of FIG. 69 and the upper housing of theradiation dosimeter being raised above the lower housing of theradiation dosimeter;

FIG. 110 is an image showing the radiation dosimeter and dosimeterdrawer of FIGS. 106, 107 and 108 fully pushed into the ready regionhousing;

FIG. 111 shows the dosimeter reader in the state shown in FIG. 110 inwhich the housing cover is removed to show interior details includingthe radiation dosimeter in the ready region housing housing;

FIG. 112 shows the radiation dosimeter reader in the state shown in FIG.111 with the upper housing removed to show the slider of the OSL readerengaging the dosimeter sled of the radiation dosimeter;

FIG. 113 shows the dosimeter sled of FIG. 112 being pulled out of thelower housing of the radiation dosimeter and being pulled into the OSLreader housing by the puller pusher of the OSL reader;

FIG. 114 shows the dosimeter sled of FIG. 113 pulled by the slider ofthe OSL reader to a reading position for the comparator OSL filter ofthe dosimeter sled;

FIG. 115 shows the dosimeter sled of FIG. 114 pulled by the slider ofthe OSL reader to a reading position for the reference OSL filter of thedosimeter sled;

FIG. 116 is a graph of a photon energy response of Al, CuT and CuPfilters;

FIG. 117 is a graph of a photon energy response of Al, CuT and CuPfilters relative to Cs-137; and

FIG. 118 is a graph of a photon energy response of Al and CuP filtersrelative to CuT.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Definitions

Where the definition of terms departs from the commonly used meaning ofthe term, applicant intends to utilize the definitions provided below,unless specifically indicated.

For the purposes of the present invention, directional terms such as“top”, “bottom”, “upper”, “lower”, “above”, “below”, “left”, “right”,“horizontal”, “vertical”, “upward”, “downward”, etc., are merely usedfor convenience in describing the various embodiments of the presentinvention.

For the purposes of the present invention, a value or property is“based” on a particular value, property, the satisfaction of acondition, or other factor, if that value is derived by performing amathematical calculation or logical decision using that value, propertyor other factor.

For the purposes of the present invention, the term “angle of incidence”refers to the angle between the direction of the radiation trajectoryand a line perpendicular (normal) to the detector surface.

For the purposes of the present invention, the term “close proximity”refers to a distance comparable with the penetration range of chargedparticles in a particular medium.

For the purposes of the present invention, the term “comparator OSLsensor” refers an OSL sensor that includes a reference filter materialand is used to adjust the dose determined by the reference sensor atvery low energies of x-rays or gamma rays. In some embodiments of thepresent invention, the reference filter material of a comparator OSLsensor may be applied as a thin coating on an OSLM or be mounted as athin film or disc adjacent to the OSLM in a reference OSL sensor OSLsensor. In one embodiment of the present invention, the reference filtermaterial may be in the form of a disc that is mounted between the OSLMand the base of a cylindrical-cup shaped filter in which the OSLM ismounted. In one embodiment of the present invention, the OSLM of acomparator OSL sensor may be mixed with the reference filter material sothat the OSLM is embedded or suspended in the reference filter material.

For the purposes of the present invention, the term “converter material”refers to a converter material that can convert non-ionizing neutronradiation into recoil or knockout protons, which can be detected by anOSL sensor or include a fluorescent nuclear track detector (FNTD). Anexample of a “converter material” is high-density polyethylene (HDPE).Another example of a “converter material” is polyethylene (PE). In someembodiments of the present invention, a converter material may beapplied as a thin coating on an OSLM or be mounted as a thin film ordisc adjacent to the OSLM of a neutron-sensitive OSLM sensor. In oneembodiment of the present invention, the converter material may be inthe form of a disc that is mounted between the OSLM and the base of acylindrical-cup shaped filter in which the OSLM is mounted. In oneembodiment of the present invention, the body of a dosimeter sled madeof a converter material such as HDPE or PE so that the entire dosimetersled may act as converter material for an OSLM or an FNTD mounted in thedosimeter sled. In another embodiment of the present invention, the OSLMmay be mixed with the converter material so that the OSLM is embedded orsuspended in the converter material.

For the purposes of the present invention, the term “cylindricalcup-shaped” refers to a filter having the general shape of a rightcylinder with the top or bottom of the cylinder removed i.e. the filterhas a disc-shaped bottom or top and a cylindrical wall extendingtherefrom. The walls, top or bottom may be formed from the same materialor different materials depending on the angular and energy compensationresponse to radiation desired for the dosimeter.

For the purposes of the present invention, the term “dosimetricparameter” refers to the value or the number determined from processingthe fluorescent image or signal of irradiated luminescent material andis directly related to the dose of radiation absorbed by the detector.

For the purposes of the present invention, the term “energy compensatingmaterial” refers to a material that when placed between an OSLM and asource of gamma radiation or x-ray radiation alters the response over arange of gamma energies or x-ray energies compared to the OSLM exposedwith no compensating or filtering material. Examples of energycompensating materials are copper and aluminum.

For the purposes of the present invention, the term “fast neutron”refers to the conventional meaning of the term “fast neutrons”, meaningneutrons with energies above 10 keV.

For the purposes of the present invention, the term “filter” refers toany structure that is located between a radiation sensing material, suchas an OSLM, and a source of radiation and affects the radiationexperienced by the radiation sensing material. For example, a filter maybe an energy compensating filter, a converter, a reference filter, aconformal disc etc. In one embodiment of the present invention, theenergy compensating filter may be a cylindrical cup-shaped filter.Although the filters of the present invention are primarily describedbelow as being used with optically stimulated luminescent materials, thefilters of the present invention may be used with other types ofradiation sensing materials, such as thermoluminescent dosimetry (TLD)materials. In one embodiment of the present invention in which an OSLsensor comprises an OSLM disc mounted in a cup-shaped filter, one ormore filter material discs may be located between the OSLM disc and thebase of the cylindrical cup-shaped filter. Each of the filter materialdiscs would constitute a filter.

For the purposes of the present invention, the term “filter material”refers the material or materials of which a filter is comprised. Forexample, depending on the type of filter, a filter material may be anenergy compensating material, a converter material, a reference filtermaterial, a conformal material, etc. Although the filter materials ofthe present invention are primarily described below as being used withoptically stimulated luminescent materials, the filter materials of thepresent invention may be used with other types of radiation sensingmaterials, such as thermoluminescent dosimetry (TLD) materials.

For the purposes of the present invention, the term “heavy chargedparticle (HCP)” refers to nuclei or ions with masses equal to or greaterthan a proton. Some representative, but nonlimiting examples of heavycharged particles include: alpha particles, tritium ions, protons,recoil protons, etc.

For the purposes of the present invention, the term “indirectly ionizingradiation” refers to x-rays, gamma rays or neutrons.

For the purposes of the present invention, the term “ionizing radiation”refers to any particulate or electromagnetic radiation that is capableof dissociating atoms into a positively and negatively charged ion pair.The present invention may be used to determine doses of both directlyionizing radiation and indirectly ionizing radiation.

For the purposes of the present invention, the term “irradiation” refersto the conventional meaning of the term “irradiation”, i.e., exposure tohigh energy charge particles, e.g., electrons, protons, alpha particles,etc., or electromagnetic radiation of wave-lengths shorter than those ofvisible light, e.g., gamma rays, x-rays, ultraviolet, etc.

For the purposes of the present invention, the term “low penetratingradiation” refers to radiation from heavy charged particles havingpenetration range that is less than 100 microns (100μ) in a radiationsensing material or absorber. Examples of low penetrating radiation are:alpha particles, recoil protons, etc.

For the purposes of the present invention, the term “maximum penetrationrange” or “penetration range” refers to the distance in the medium atwhich a directly ionizing particle comes to rest.

For the purposes of the present invention, the term “moderated neutrons”refers to neutrons produced by slowing fast neutrons by a hydrogen ordeuterium containing moderator and having a large contribution of lowenergy neutrons in the energy range from about 0.025 eV to about 10 keV.

For the purposes of the present invention, the term “neutron to protonconverter” refers to a hydrogen-containing material, such ashigh-density polyethylene (HDPE) that may be used to convertnon-ionizing neutron radiation into recoil or knockout protons, whichcan be detected by a radiation sensor.

For the purposes of the present invention, the term “neutron-sensitiveOSL sensor” refers to an OSL sensor that detects neutrons. Aneutron-sensitive OSL sensor may also detect other types of radiationsuch as x-ray and gamma rays.

For the purposes of the present invention, the term “OSL reader” refersto a device that emits a wavelength of light that stimulates an OSLM inan OSL sensor to emit light. Under a specified stimulation regime(continuous stimulation, reading wavelength and intensity, and pulsedstimulation with various pulse durations, pulse frequency, pulse shapeand time between pulses) the intensity of the emitted light isproportional to the radiation exposure in a range from about 0.01 mGy (1mrem) to over about 100 Gy (10,000 rads).

For the purposes of the present invention, the term “OSL sensor” refersto a radiation sensor that is made from or includes an OSLM. OSL sensorsmay be read using an OSL reader.

For the purposes of the present invention, the term “passive detection”refers to the detection technique that does not require any activeelectronic circuitry and a supply of electrical power to detect theradiation and/or integrate the radiation absorbed dose.

For the purposes of the present invention, the term “penetrating photonradiation” refers to short wavelength electromagnetic radiation withenergies equal to or higher than 10 keV as might originate fromradioactive nuclear decay, from space or produced by accelerating ordecelerating of charge particles, for example, in an X-ray machine or inan accelerator.

For the purposes of the present invention, the term “penetrating betaradiation” refers to electrons with energies equal to or greater than 10keV as might originate from radioactive nuclear decay, from space,produced by radiation-induced ionization of atoms or by acceleration inan electric field.

For the purposes of the present invention, the term “portion” refers toany portion of an object or material, including the entire object andmaterial. For example, a converter that covers a “portion” of aluminescent material may cover part or all of one or more surfaces ofthe luminescent material.

For the purposes of the present invention, the term “radiationdosimetry” refers to the conventional meaning of the term “radiationdosimetry”, i.e., the measurement of the amount of radiation doseabsorbed in a material, an object or the body of an individual.

For the purposes of the present invention, the term “radiation sensingmaterial” refers to a material used to sense radiation in a radiationsensor. Examples of radiation sensitive materials including opticallystimulated luminescent materials for OSL sensors, thermoluminescentmaterials for thermoluminescent dosimetry (TLD) sensors, etc.

For the purposes of the present invention, the term “recoil protons”refers to those protons that are generated by the collision of neutronswith a converter containing a source of hydrogen atoms, e.g.polyethylene or high-density polyethylene.

For the purposes of the present invention, the term “reference filtermaterial” refers to a non-hydrogen containing, carbon based materialwith certain optical absorption and reflection properties that has afiltering effect on x-rays and gamma rays that is similar to theradiation filtering and optical absorption and reflection effects of anorganic converter material on x-rays and gamma rays. For example, the“reference filter material” fluorinated plastic polytetrafluoroethylene(sold under the trade name Teflon® by DuPont), which has a filteringeffect on x-rays and gamma rays that is similar to the neutron-to-protonconverter material high-density polyethylene (HDPE). A reference filtermaterial acts on both optical stimulation and luminescence light and isused to enhance the effectiveness of the method according to oneembodiment of the present invention.

For the purposes of the present invention, the term “reference OSLsensor” is an OSL sensor that includes a reference filter material andis used to determine the effects of a converter material on x-ray andgamma ray detection by another OSL sensor that is identical to thereference OSL sensor, except for the substitution of the convertermaterial for reference filter material. In some embodiments of thepresent invention, the reference filter material of a reference OSLsensor may be applied as a thin coating on an OSLM or be mounted as athin film or disc adjacent to the OSLM in a reference OSL sensor. In oneembodiment of the present invention, the reference filter material maybe in the form of a disc that is mounted between the OSLM and the baseof a cylindrical-cup shaped filter in which the OSLM is mounted. Formany radiation dosimeters, which employ three OSL sensors arranged in arow, the best angular response for the radiation dosimeter is oftenimproved when the reference OSL sensor is the center OSL sensor. In oneembodiment of the present invention, the OSLM of the reference OSLsensor may be mixed with the reference filter material so that the OSLMis embedded or suspended in the reference filter material.

Description

In existing personal radiation monitoring devices, the radiation sensorsare generally captured in a holder containing one or more filters thatalter the amounts, energies and types of radiation able to reach thesensors. These filters typically sandwich the sensors to achieve correctassessments when the radiation enters the dosimeter from various anglesof incidence. To analyze the sensors, they must be removed from betweenthe filters and holder and physically presented to the processing systemrequired to elicit the quantitative attribute exhibited by the sensorfollowing exposure to radiation.

For example to analyze a film dosimeter generally involves the followingsteps: 1. Removing the film packet from the holder where it issandwiched between the filters; 2. Unwrapping protective packaging thatprotects the film from light fogging and physical damage; 3. Developingthe films in chemicals; 4. Measuring the density of the film by placingit between a light source and a light detector and comparing thetransmission of light through the film to a reference condition wherethere is nothing placed between the light source and light detector,and; 5. Relating the density to radiation exposure in one or more areasof the film corresponding to the areas where the film was sandwichedbetween the filters.

Similarly radiation sensors based on thermoluminescent dosimetry (TLD)must be removed from the holder and their position between the filtersand presented to a very high temperature environment necessary to causethe sensor to emit luminescence and measure the amount of suchluminescence whose intensity is proportional to the radiation dose. Therequired temperatures will typically burn the holder and any identifyinglabels, thereby necessitating the removal of the sensors from the TLDdosimeter. Most common metallic filters also create incandescence andother interfering light at the very high temperatures, e.g. 200 to 300°C. The disassembly process involves a number of mechanical steps thatcreate operating inefficiencies. Also, because of the multiple steps inthe disassembly process for a TLD dosimeter, a complex identificationsystem is required to link a specific TLD sensor or sensors to theholder that is needed to establish an unbroken chain of custody wherebythe results of the radiation dose analysis can be related to aparticular person or place being exposed to radiation. The sequence ofsteps in disassembling a TLD dosimeter also introduces a risk ofdamaging or losing the sensors during the movement of the sensors to theprocessing instruments and incorrect reassembly of the dosimeter whensuch sensors can be reconditioned for reuse.

In contrast, radiation sensors based on optically stimulatedluminescence, OSL sensors, only require an optical path whereby astimulating beam of light can illuminate the OSL sensor(s) and theresultant radiation induced luminescence can be routed back through thesame or alternate optical path to a light detector such as aphotomultiplier tube that quantifies the amount of luminescent light. Inone embodiment, the invention employs an optical path whereby anexternal beam of light can enter the interior of the holder, illuminateeach OSL sensor and enable the luminescent light to exit the holderalong the same optical path without need to remove the sensors fromtheir normal position with respect to any filters or convertingmaterials. The optical path may be either an optical fiber or anuninterrupted air channel through which light can travel.

For more information on OSL materials and systems, see, U.S. Pat. No.5,731,590 issued to Miller; U.S. Pat. No. 6,846,434 issued to Akselrod;U.S. Pat. No. 6,198,108 issued to Schweitzer et al.; U.S. Pat. No.6,127,685 issued to Yoder et al.; U.S. patent application Ser. No.10/768,094 filed by Akselrod et al.; all of which are incorporatedherein by reference in their entireties. See also Optically StimulatedLuminescence Dosimetry, Lars Botter-Jensen et al., Elesevier, 2003;Klemic, G., Bailey, P., Miller, K., Monetti, M. External radiationdosimetry in the aftermath of radiological terrorist event, Rad. Prot.Dosim., in press; Akselrod, M. S., Kortov, V. S., and Gorelova, E. A.,Preparation and properties of Al₂O₃:C, Radiat. Prot. Dosim. 47, 159-164(1993); and Akselrod, M. S., Lucas, A. C., Polf, J. C., McKeever, S. W.S. Optically stimulated luminescence of Al₂O₃:C, Radiation Measurements,29, (3-4), 391-399 (1998), all of which are incorporated herein byreference in their entireties.

Passive sensors, such as film, TLD or OSL sensors as described above,accumulate and store the dose within the molecular structure of thesensor without any need of electrical power. This characteristic makespassive sensors ideal for situations where the risk of a powerinterruption is unacceptable. Optically stimulable crystals andradiation scintillation sensors have been connected to the ends of fiberoptic cables so that the sensors can be attached to the measurementinstrument without removing the sensors from their locations in theradiation field. The sensors are integrally sealed to the ends of theoptical fiber to prevent stray light from interfering with themeasurement. The optical fibers connect to the light measurementinstrument via a mechanical connector that mates the fiber to theoptical pathway created in the instrument. As a single sensor isattached to a single fiber, radiation dosimeters requiring multiplesensors must have multiple fiber connectors that must be individuallylinked to the photonics system in the instrument. The physical size ofthe connectors and the need to cap the free end when not joined to themeasurement instrument make dosimeters with multiple fiber leadsimpractical and inconvenient for the wearer.

In one embodiment of the present invention, the design of the radiationdosimeter enables the OSL sensors to be enclosed with the dosimeterbeing analyzed, until the OSL sensors are read. The radiation dosimeteralso provides a means of protecting the OSL sensors and light path fromdirt or other things that may alter or affect the amount of stimulatingand luminescent light able to travel to and from the OSL sensor(s) andthe analytical instrument (dosimeter reader). The design permits the OSLsensors to be permanently embedded in a sled so that the sensor(s) canbe carried by the sled to the stimulation light source and luminescencecollector without having to separate the OSL sensors from the sled. Thisaids chain of custody because the singularity of the dosimeter sled andOSL sensors allows the same identification label or tag to apply to allparts. The design also reduces the number of parts and mechanicalcomplexity of having a means to open dosimeter so that sensors can beremoved for analysis. Also, because the sled also contains the filters,the positional arrangement of all the critical elements of the dosimeterare fixed and not disassembled for analysis.

In one embodiment, the present invention eliminates a number of physicalsteps thereby improving productivity and enabling simpler automatedhandling of large numbers or dosimeters. The design allows betterexploitation of the very fast stimulation and luminescence processesthat make the analysis of optically stimulated luminescence radiationsensors a very rapid analytical method, again providing greaterproductivity in terms of units analyzed per unit of time. Radiationsensors based on measuring electrical signals such as current, voltageor resistance that are changed as a result of exposure to radiation canbe connected to a measurement instrument such as an electrometer,voltmeter or pulse counter via wires or other types of conductingpathways. Therefore the sensors may be packaged permanently into thedevice worn by the user. Such devices generally require a source ofpower to establish the voltage gradients needed to attract theionization created by the radiation in the sensor to an electrode orsolid-state collector. These types of devices are generally classed asactive in that they can provide an instantaneous indication of theradiation exposure rate. If provided a memory capability, active devicescan integrate the rate data to provide an estimate of the accumulateddose.

One of the most difficult tasks in radiation dosimetry is discriminationof the dose created by different radiations, especially neutrons.Accordingly, the neutrons need to be converted to directly ionizingradiation, such as alpha particles, energetic protons, etc., to bedetected by such crystals. For dosimetry of fast neutrons, recoilprotons from hydrogen rich plastics, such as high-density polyethylene,are preferred because they are similar to the interactions with waterthat occur in the body. These converters of neutrons may be associatedwith, attached to or otherwise in contact with the luminescent material,may be mixed or merged with the luminescent material or may be even bepart of or incorporated into the luminescent material. Alpha and betaparticles and protons originated from radionuclides and acceleratorfacilities, as well as heavy charged particles of cosmic rays, usuallydo not need any conversion.

In one embodiment of the present invention, each OSL sensor comprises anassembly composed of one or more cylindrical cups that act as energycompensating filters that alter the energy or gamma rays and x-rays ableto reach the OSL material (OSLM). The cups can be formed from onematerial or have a top and sides of different materials depending on theangular response desired for the dosimeter. The thickness of the top andwalls may be different from each other depending on the angular responsedesired for the dosimeter. The shape of the cup walls and top need notbe flat or uniform but can be curved and of varying thickness dependingon the angular response desired. The cups may be designed in concertwith the upper and lower housings as these also act as energycompensating filters.

In one embodiment of the present invention, the radiation dosimeter maybe worn in a fashion similar to a watch. For such a radiation dosimeter,the curve structured of the upper housing combined with the rightcylinder cups permits this dosimeter to be worn on the wrist and stillassess the dose to the body as if the dosimeter were worn on the body.

In one embodiment of the present invention, the lower housing containsenergy compensating filters that are flat either as discs aligning withthe openings of the cup or as a plate extending all dimensions of thecup openings. The sequence of the metal used in the cups imparts theoptimum energy shaping as the lower atomic number elements removephotoelectrons created in the higher atomic number elements by lowerenergy x-rays. The photoelectrons can impart an undesired response inthe OSLM. The cups may be held in place on the sled by compression fit,adhesives or molded in place so that the sled encompasses the cups.

When multiple cups are used for one sensor, they can be held togethervia a crimping action, compression fit or adhesive. In many embodimentsof the present invention, no more than two cups would be used with onecontained by the other. This keeps the overall height, cost and assemblyat practical values.

Within the cup are converting filters that convert the indirectlyionizing radiations into directly ionizing particles, mainly electronsfrom gamma rays and x-rays, and recoil protons for neutrons. Inaddition, the converters create a reflective condition whereby thestimulation light passing through the OSLM is reflected into the OSLMthereby gaining more effective use of the stimulation light. Similarly,the converters reflect the luminescence light traveling inwards into thecup back out into the cup opening and into the light pipe of thephoto-engine in the dosimeter reader.

In one embodiment of a neutron-sensitive OSL sensor of the presentinvention, the thickness of the HDPE converter that converts theneutrons into recoil protons and the gamma rays/x-rays into electrons isoptimized at 1 mm to create a maximum number of recoil protons andelectrons. A separate thin piece of HDPE may be added to provide bettercontact between the OSLM and HDPE.

In one embodiment of the present invention, the thickness of the PTFEused in the reference OSL sensor and the comparator OSL sensor is suchthat it converts the gamma rays/x-rays into a similar number ofelectrons. In this case its thickness is also 1 mm. The tolerance of thethicknesses of both converters may be ±0.1 mm

The converters and filters may be retained inside the cups either byadhesives, compression fit or retaining rings that also retain the OSLMin contact with the converters. The retaining ring may be a 0.6 mmdiameter wire that fully wraps around the interior diameter of the innercup. The retaining ring defines the optical readout area of thestimulation light illuminating the OSLM.

Although the converters and filters described below and shown in thedrawings are flat in other embodiments, the converters may be parabolicto enhance the optical reflection into the light pipe but with addedcost.

The combined construction of the energy compensating filter cups andradiation converting filters is such that when mounted into the sled,all of the OSLM is at the same height in the sled and therefore the samedistance from the exit of the light pipe of the optical engine.

Each sensor may be individually calibrated as the reflection and lightabsorption properties of the HDPE and PTFE are slightly different. Thisalso permits visual distinction of the sensors needed for accurateassembly of the dosimeter.

The grain size of the aluminum oxide particles in an OSLM according toone embodiment of the present invention may be selected based on therange of the recoil protons in the aluminum oxide. Based on Monte Carlosimulations and experimental confirmation tests, this grain size isbetween 30 and 40 microns for the fast neutron environments of mostconcern in radiation protection dosimetry. Once the recoil protons havedeposited their energy in the aluminum oxide grain, any greater sizewould not increase the proton response but since the electrons have agreater range, the response due to the gamma rays/x-rays would increasethereby reducing the neutron to gamma ray/x-ray signal ratio.Conversely, smaller grains would not fully capture the recoil protonenergy thereby also reducing the neutron to gamma ray/x-ray signalratio.

The coating of the aluminum oxide grains onto a clear film may be donewith binders that have minimal hydrogen so that the reference sensorresponse is only due to gamma rays and x-rays.

In one embodiment of the present invention, a minimal binder coating isused on top of the grains so as to not to interfere with the recoilprotons depositing their energy into the aluminum oxide.

In one embodiment of the present invention, the film on which thealuminum oxide is coated may be transparent to blue and green light andhave a thickness ranging between 0.05 and 0.15 mm.

In one embodiment of the present invention, the OSL sensors are mountedin a dosimeter sled that slides in contact with the plate in the OSLreader to which a photo-optical engine of the present invention isattached. The dosimeter sled, combined with the OSL sensors, maintainsthe OSLM material in each of the OSL sensors at a constant distance fromthe exit of the optical light pipe of the OSL reader to assure uniformstimulation and collection of luminescence light. In one embodiment ofthe present invention, an end side of the dosimeter sled is curved toensure that the circular optical light pipe is completely blocked whenthe OSL sensor mounted closest to the curved end side is read.

In one embodiment of the present invention, the dosimeter sled in whichthe OSL sensors are mounted may be made of PE or HDPE allowing part ofits surface to be used to convert the neutrons to recoil protons in thatarea where the FNTD sensor is mounted on the underside recess in thesled.

In one embodiment of the present invention, the centers of each sensormay be aligned along a straight line parallel to the long axis of thesled and along the axis of travel into and out of the rail system in theOSL reader of the dosimeter reader that guides the slide and in turn thesensors over the light pipe of the photo-engine in the OSL reader.

In one embodiment of the present invention, the dosimeter sled may beengraved with an identification number that is reproduced in an RFIDtag.

In one embodiment of the present invention, the dosimeter sled has arecess over the comparator OSL sensor where the RFID tag is placed. TheRFID tag may be held in place by an adhesive transfer tape such as 3Madhesive tape with 300SLE adhesive or alternatively with a UV curableadhesive liquid placed along the edge of the tag. The placement of theRFID tag is such that the metal filters do not impede the RF fieldcreated by the RFID tag reader thereby permitting correct reading andwriting to the RFID tag.

In one embodiment of the present invention, the OSL sensors are mountedin openings in the dosimeter sled that include respective ledges thatlocate the height of the OSL sensors. The combination of these ledgesand the cylindrical-cup shaped filters are also designed to maintain theOSLM in each OSL sensor at the same height.

In one embodiment of the present invention, in addition to the three OSLsensors described above, the radiation dosimeter may also include afluorescent nuclear track detector (FNTD) mounted in the dosimeter sled.The FNTD provides an alternative method of dosimetry under alternateconditions of analysis. Examples of suitable fluorescent nuclear trackdetectors are described in U.S. patent application Ser. No. 12/258,035to Akselrod, et al., entitled “METHOD OF LUMINESCENT SOLID STATEDOSIMETRY OF MIXED RADIATIONS” filed Oct. 24, 2008, the entire contentsand disclosure of which is incorporated herein by reference.

In some embodiments of the present invention, in addition to the threeOSL sensors described above or in place of one of the OSL sensorsdescribed above, the dosimeter sled may include an OSL sensor that has asecond type of OSLM that is different from the OSLM in the other OSLsensors.

In one embodiment of the present invention, the underside of thedosimeter sled may include a recess that houses an FNTD (fluorescencenuclear track detector) or a polyallyldicarbonate plastic (PADC soldunder the trade name CR-39) to alternately assess the dose fromneutrons. Within the recess are two wells into which are placed a pieceof PTFE and a piece of LiF or Li loaded plastic. These align with theupper surface of the recess creating a uniform surface on which the FNTDor PADC is placed. They are held into place either by a compression fitor with an adhesive. The PTFE acts as a reference converter in a waysimilar to its role with the OSL sensors. The HDPE surface created bythe sled acts as a neutron converter similar to the way that an HDPEdisc may be used as a converter material disc in an neutron-sensitiveOSL. The lithium converter preferentially converts thermal and slowenergy neutrons into recoil alpha particles and tritium ions from theLi-6(n,α)H-3 reaction. Both the FNTD and the PADC are held in place bysmall tabs that hook over the edges of the sensors. The FNTD or PADC maybe engraved with ID numbers matching that of the sled and RFID tag.

In one embodiment of the present invention, the long sides of thedosimeter sled have protruding rails that are inserted intocorresponding slots in the lower housing. The rails have beveled edgesto permit easy movement into and out of the lower housing and provide aspace for small amounts of dirt or dust to accumulate without impedingthe sliding motion.

One rail has semicircular notches that align with the centers of each ofthe sensors. These permit a photodiode to sense when the sled is in thecorrect position for analysis in the OSL reader. The correct position isthat which allows the stimulation light to fully illuminate the area ofthe OSLM in the sensor.

The trailing edge of the sled has a semicircular edge that providesextra light protection when reading the third sensor in the OSL reader.The rounded edge provides added extension of the sled beyond the edge ofthe light pipe thereby preventing stray light from entering the lightpipe from the trailing edge of the sled into and out of the OSL reader.Some embodiments may omit this feature.

The leading edge has a U-shaped detent and a tang that engages with atang and U-shaped detent, respectively, on a slider that pulls thedosimeter sled into and out of the housing for the OSL reader.

The openings over the sensors permit visual and electronic verificationof the correct placement of the sensors by automated assembly equipment.An electrical contact is made to verify correct placement and a colorsensor may be used to verify that a filter of a sensor is copper insteadof aluminum or vice versa.

The upper housing is circular but may have molded facets to providevisual differentiation as to where the dosimeter is to be worn, e.g.circle for wrist, hexagonal facets for wearing on the body, etc.

The upper housing may have opposed loops of slots into which a strap ofbelt may be inserted for wearing on the wrist or other body part. Oneloop may be omitted so that a clip is inserted through the slot forattachment to clothing like an identification badge.

The housing will have a product identification or model number embossedor engraved.

The housing may have an alignment symbol to aid in properly positioningthe dosimeter onto the dosimeter drawer of the dosimeter reader.

The housing may have a curved arrow showing the direction of rotation todisengage the threads holding the upper and lower housings together.

The housing may be constructed of polyoxymethylene (POM trade nameDelrin® by Dupont), polycarbonate (Lexan), acetylbutylstyrene (ABS) orother suitable plastic material.

The upper housing will have a flat inner surface at an angle of 15 to 25degrees from the bottom plane of the housing below the threads that willmate to a sealing material located on the lower housing so as to providea watertight seal.

The upper housing will be threaded so that a 90° counterclockwiserotation will disengage the housing from the lower housing permittingthe two pieces to be separated from each other.

In one embodiment, the present invention provides a radiation dosimeterwith three OSL sensors: (1) a neutron-sensitive OSL sensor that sensesgamma, x-ray and neutron radiation, (2) a reference sensor that sensesonly x-ray and gamma radiation and (3) a comparator OSL sensor for thereference sensor. The neutron-sensitive OSL sensor includes an OSLM thatis mounted in an inner filter made of a first energy compensatingmaterial, such as aluminum. The inner filter is in turn mounted in anouter filter made of a second energy compensating material, such ascopper. Placed between the inner compensating filter and the OSLM,either as a thin disc, thin layer or thin coating, is a convertermaterial, such as high-density polyethylene, that converts neutrons intorecoil protons that can be sensed by the neutron-sensitive OSL sensor.The reference OSL sensor is identical to the neutron-sensitive OSLsensor, except that instead of the converter material being placedbetween the inner compensating filter and the OSLM, a reference filtermaterial, such as polytetrafluoroethylene, is placed between the innercompensating filter and the OSLM either as a thin disc, a thin layer oras a thin coating on the OSLM. The comparator OSL sensor is identical tothe reference OSL sensor, except that the comparator OSL sensor does notinclude the outer filter of the reference OSL sensor.

In one embodiment, the neutron-sensitive OSL sensor, the reference OSLsensor, and the comparator OSL sensor may be mounted in a dosimeter sledthat may be slid out of the radiation dosimeter to allow the three OSLsensors to be read using an OSL reader. The design of the dosimeter sledallows the three OSL sensors to be read from the same side, the exposedside of each OSL sensor where there is no filter covering the OSLM ofthe OSL sensor. Although in the embodiments shown below, the three OSLsensors are mounted in the dosimeter sled in the order: (1)neutron-sensitive OSL sensor, (2) reference OSL sensor, and (3)comparator OSL sensor, the three OSL sensors may be mounted in thedosimeter sled in any order.

In one embodiment of the present invention, the OSLM used in the OSLsensors is a specialized carbon-doped aluminum oxide (Al₂O₃:C) materialmanufactured by Landauer, Inc. (Glenwood, Ill.), and is similar to thatmarketed in dosimeters with trade names LUXEL+ and INLIGHT. The OSLMconsists of specially formulated, proprietary, powderized Al₂O₃:C. Foruse in the OSL sensors of the present invention, the Al₂O₃:C materialmay be in the form a disc-shaped pellet.

Exposure of the Al₂O₃:C material in each of the three OSL sensors toionizing radiation releases electrons that are trapped in defects in thematerial's crystal structure. The electrons are released from the trapswhen stimulated with 520±10 nm wavelength light (i.e. green). As theyreturn to the ground state, 420±10 nm wavelength light (i.e. blue) isemitted. It should be noted that other light wavelengths could beemployed, as could a pulsed stimulation system in reading the OSLsensors of the present invention.

The dosage of gamma ray and x-ray radiation received by the dosimeterand the individual who has been wearing the dosimeter may be determinedfrom the emitted light from the second or reference OSL sensor and maybe modified based on the results of reading the third comparator OSLsensor. The dosage of neutron radiation may be determined by subtractingthe dosage value from reading the second OSL sensor from the dosagevalue from reading the first OSL sensor and multiplying the result by acalibration factor appropriate for the expected neutron energy spectrum.

In one embodiment of the present invention, a radiation dosimeter orpart of a dosimeter, such as a dosimeter sled, includes an RFID tag. TheRFID tag includes a radiofrequency (RF) antenna that allows the RFID tagto communicate with the RF antenna of an RFID tag reader to allowinformation/data to be read from the RFID tag by the RFID tag reader andto allow the RFID tag reader to store information on the RFID tag. Inone embodiment of the present invention, the RFID tag includes anon-volatile data storage device, such as flash memory, that allows theRFID tag to store information about the radiation dosimeter and thewearer of the radiation dosimeter that enables the reading out of theradiation dosimeter by any reader without having to access a database toretrieve data needed to calculate the dose. When the RFID tag is part ofa dosimeter sled, the RFID tag may be read while the sled is in thedosimeter. The dosimeter does not need to be disassembled nor thedosimeter sled removed to read data from and/or write data to the RFIDtag. The RFID tag may be read when the dosimeter sled is in a readingposition for one of the OSL sensors of the dosimeter sled or at aseparate reading position for the RFID tag.

Although the RFID tag of the present invention is described for use withparticular radiation dosimeters in the embodiments of the presentinvention are described below, the RFID tag may also be used with othertypes of radiation dosimeters. For example, the RFID tag may be usedwith badge-type, case-type and slide-type radiation dosimetersmanufactured and sold by Landauer, Inc under the trade name InLight™.The RFID tag may also be used with radiation dosimeters employing avariety of dosimeter materials and/or dosimeter reading methods,including the dosimeter materials and dosimeter reading method describedin: U.S. Pat. No. 5,354,997 to Miller, entitled “Method for IncreasedSensitivity of Radiation Detection and Measurement,” issued Oct. 11,1994; U.S. Pat. No. 5,567,948 to Miller, entitled “Composite MaterialDosimeters,” issued Oct. 22, 1996; U.S. Pat. No. 5,569,927 to Miller,entitled “Composite Material Dosimeters,” issued Oct. 29, 1996; and U.S.Pat. No. 5,731,590 to Miller, entitled “Metal Oxide Composite DosimeterMethod and Material,” issued Mar. 24, 1998, and the entire contents anddisclosures of these patents are incorporated herein by reference.

The RFID tag may store the results of the last several readouts, therebyenabling the dose history experienced by the wearer to be retrieved. TheRFID tag may carry identification, date and time data to establish achain of custody regarding who was assigned the dosimeter and whencertain actions were performed on the dosimeter. In one embodiment ofthe present invention, the RFID tag may carry the following information:identification information for the dosimeter model, dosimeter serialnumber and an identification number for the individual to whom thedosimeter is assigned, calibration data for each OSL sensor, date andtime information needed to estimate the buildup of background radiationdose, the total radiation dose and the dose from gamma rays and the dosefrom neutrons, date and time information regarding the assignment of thedosimeter to an individual, date and time information when the dosimeterwas readout, and reader quality control data depicting the operabilityof the dosimeter reader during the analysis of the dosimeter includingthe unique reader identification number.

The RFID tag of the present invention may be read and written to usingan appropriate RFID antenna and deciphering code either by the dosimeterreader or by a stand-alone RFID tag reader connected to a PC or otherdata input device. When the dosimeter is returned to a laboratory fromthe field, the dose results may be separately read out to verify thefield results and the recent history of the dosimeter results obtainedin the field reviewed to establish an accredited radiation dose recordfor archiving.

In one embodiment of the present invention, the RFID tag enables thedosimeter to be analyzed in remote areas where there is no access todatabases containing information needed for the correct analysis of thedosimeter. The RFID tag carries the history of the analysis of thedosimeter so that a dose reconstruction can be performed. The RFID taghas a limited range of readout to avoid detection of the dosimeterduring covert operations.

In one embodiment, the dosimeter reader may communicate with a databaseseparated from the dosimeter reader. The dosimeter reader maycommunicate with the separate database in a variety of ways such as:wireless communication, communicating via an optical fiber,communicating over a wire, communicating over the Internet,communicating over a phone line, etc.

In some embodiments of the present invention a dosimeter may be given toand worn by an individual before the dosimeter is assigned to theindividual in the database. In such cases, the database may be updatedwith the name and other identification such as social security number,dog tag number, etc., for the individual to whom the dosimeter has beenassigned at a later date. The database may even be updated the firsttime that the dosimeter is read by a dosimeter reader.

In one embodiment, the dosimeter reader of the present invention isbattery operated and can be moved during analysis. The dosimeter readerdisplays the results of the analysis, performs Pulsed OpticallyStimulated Luminescence (POSL) processes, stores results of analyses,writes results of dosimeter analysis to an RFID chip on the dosimetersled, has an output mechanism, such as a USB plug, whereby data may bedownloaded into a remote database or PC and reader settings may beuploaded to the dosimeter reader. The dosimeter reader may belight-weight and/or water-tight and/or floatable. The dosimeter readermay be read out at various angles from the horizontal and includes adisplay and buttons for operation.

In one embodiment of the present invention, the dosimeter readerincludes stimulation light monitoring and ambient light monitoring.Stimulation light monitoring may be conducted by a photodiode to which afraction of the stimulation light is routed. The response of thephotodiode is monitored and compared to a reference value obtained forthe correct stimulation light level. Ambient light monitoring may beconducted by performing the luminescence counting routine withoutapplying any stimulation light to the OSL sensor. The dosimeter readerof the present invention may employ pulses of varying duration andfrequency. The dosimeter reader may also check for luminescenceintensity to select an alternative POSL scheme. Luminescence intensitymay be used to select an alternative POSL scheme by performing theanalytical process for a small fraction of the normal analysis time andcomparing the result to a reference value that instructs the reader tooperate the stimulation light at a given frequency and pulse durationthat increases or decreases the luminescence light created by thestimulation light thereby maintaining an optimum amount of light for thelight sensing system e.g. photomultiplier tube. The measurement off theluminescence intensity may be very brief, i.e. less than about 10% ofthe time required to read an OSL sensor.

FIGS. 1 and 2 show a radiation dosimeter 102 according to one embodimentof the present invention including an upper housing 104 and a lowerhousing 106 mounted in upper housing 1. FIG. 1 shows bottom 112 ofradiation dosimeter 102, and FIG. 2 shows top 114 of dosimeter 102.Upper housing 104 includes a circular body 120 and two generallytrapezoidal-shaped loops 122 and 124 located on respective oppositesides 126 and 128 of circular body 120. A dashed orientation line 130 isshown drawn through the middle of and perpendicular to loops 122 and124. Lower housing 106 has three circular recesses 142, 144 and 146between opposite sides 148 and 150 of lower housing 106. A dashedorientation line 152 is shown drawn through the middle of circularrecesses 142, 144 and 146.

FIGS. 2 and 3 show upper housing top 202 and upper housing bottom 204 ofupper housing 104. Upper housing top 202 corresponds to top 114 ofradiation dosimeter 102. Loops 122 and 124 have respective openings 216and 218 through which a strap member (not shown) may be threaded so thatradiation dosimeter 102 may be worn on the wrist of an individual. Upperhousing top 202 has a flat circular upper surface 220 and includes acurved arrow 222 and a circular alignment symbol 224. Also included onupper housing 104 are etched alphanumeric identification indicia 232.Circular interior wall 234 of upper housing bottom 204 includes interiorscrew threads 236. Interior wall 234 surrounds a circular recess 242with a flat bottom 244.

The Identification indicia may identify the radiation dosimeter and/orthe individual wearing the radiation dosimeter.

The body of upper housing of FIGS. 2 and 3 is made of polyoxymethylene(POM) sold under the trade name Delrin® by Dupont. However, in otherembodiments, the body of the upper housing may be made of polycarbonate,polyethylene, styrene or other durable plastic materials.

FIGS. 4 and 5 show a lower housing top 400 and a lower housing bottom402 of lower housing 106. Lower housing 106 has a circular base 404 andan upper structure 406. Upper structure 406 has a circular exterior wall408 that has screw threads 410 spaced around the circumference thereofLower housing top 400 includes a generally punch card-shaped sled recess412 having two opposite lateral sides 414 and 416, an end wall 418perpendicular to lateral sides 414 and 416, a slanted corner wall 420and an open end 422. Lateral side 414 includes an indentation 424.Lateral side 416 includes an indentation 426. Lateral side 414 includesa groove 432 and an upper lip 434 that run along the length of lateralside 414. Lateral side 416 includes a groove 436 and an upper lip 438that run along the length of lateral side 416. Lower housing upperstructure 406 includes an upper flat surface 442 and a lower flatsurface 444. Lower flat surface 444 is exposed by sled recess 412 andthe absence of upper flat surface 442 in exposed edge region 448. Lowerhousing bottom 402 has a flat bottom surface 452, circular recesses 142,144 and 146, a C-shaped groove 454 and two lozenge-shaped recesses 456and 458. Opposite ends 462 and 464 of C-shaped groove 454 are separatedby a gap 466. Respective circular copper filter discs 472 and 474 areinserted in circular recesses 142 and 144 and serve as energycompensating filters. Copper filter discs 472 and 474 are held in placein circular recesses 142 and 144 by press fitting, by being molded inplace or by using an adhesive.

The body of the lower housing of FIGS. 4 and 5 is made ofpolyoxymethylene (POM) sold under the trade name Delrin® by Dupont.However, in other embodiments, the body of the lower housing may be madeof polycarbonate, polyethylene, styrene or other durable plasticmaterials.

FIGS. 6 and 7 show dosimeter sled 600 according to one embodiment of thepresent invention including a sled body 602, a sled top face 604 and asled bottom face 606 that are opposite each other. Sled body 602includes three openings 608, 610 and 612. Openings 608, 610 and 612include respective top portions 614, 616 and 618 and respective bottomportions 620, 622 and 624. A neutron-sensitive OSL sensor 626, areference OSL sensor 628 and a comparator OSL sensor 630 are mounted inopenings 608, 610 and 612, respectively, and are held in place bypressing neutron-sensitive OSL sensor 626, reference OSL sensor 628 andcomparator OSL sensor 630 into sled body 602. Because top portions 614,616 and 618 are smaller than respective bottom portions 620, 622 and 624of respective openings 608, 610 and 612, neutron-sensitive OSL sensor626, reference OSL sensor 628 and comparator OSL sensor 630 abutrespective circular ledges (not visible in FIGS. 6 and 7) formedopenings 608, 610 and 612 by top portions 614, 616 and 618,respectively.

Although the OSL sensors in the embodiment of the present invention ofFIGS. 6 and 7 are held in the sled by press fitting, in otherembodiments the OSL sensors may be held in place with an adhesive. Inother embodiments, the OSL sensors may be molded in place so that theOSL sensors are each fully captured by the plastic sled.

Neutron-sensitive OSL sensor 626 includes a disc-shaped pellet of OSLM632, a converter material disc (not visible in FIGS. 6 and 7), acylindrical cup-shaped inner filter 634 and a cylindrical cup-shapedouter filter 636. OSLM 632 and the converter material disc are held inplace in inner filter 634 by a retaining ring 637. The convertermaterial disc is sandwiched between OSLM 632 and inner filter 634.Retaining ring 637 is a spring-type retaining ring and is held in placein inner filter 634 by compression. When retaining ring 637 iscompressed in inner filter 634, ends 638 and 639 of retaining ring 637abut each other. Inner filter 634 is mounted and held in outer filter636 by press fitting inner filter 634 into outer filter 636. OSLM 632has a filtered side (not visible in FIGS. 6 and 7), the side of OSLM 632filtered by the converter material disc, inner filter 634 and outerfilter 636. Neutron-sensitive OSL sensor 626 has an exposed side 640,shown in FIG. 7, which allows the combined dosage of x-ray, gamma andneutron radiation to which OSLM 632 has been exposed to be read by anOSL reader. Retaining ring 637 is mounted on exposed side 640 of OSLM632. OSLM 632 comprises an Al₂O₃:C material. Inner filter 634 is made ofaluminum. Outer filter 636 is made of copper. Retaining ring 637 is madeof stainless steel. The converter material disc is a thin disc made ofhigh-density polyethylene.

Reference OSL sensor 628 includes a disc-shaped pellet of OSLM 642, areference filter material disc (not visible in FIGS. 6 and 7), acylindrical cup-shaped inner filter 644 and a cylindrical cup-shapedouter filter 646. OSLM 642 and the reference filter material disc areheld in place in inner filter 644 by a retaining ring 647. The referencefilter material disc is sandwiched between OSLM 642 and inner filter644. Retaining ring 647 is a spring-type retaining ring and is held inplace in inner filter 644 by compression. When retaining ring 647 iscompressed in inner filter 644, ends 648 and 649 of retaining ring 647abut each other. Inner filter 644 is mounted and held in outer filter646 by press fitting inner filter 644 into outer filter 646. OSLM 642has a filtered side (not visible in FIGS. 6 and 7), the side of OSLM 642filtered by the reference filter material disc, inner filter 644 andouter filter 646. OSLM 642 has an exposed side 650 that establishes anoptical pathway, shown in FIG. 7, which allows the combined dosage ofx-ray and gamma radiation to which OSLM 642 has been exposed to be readby an OSL reader. Retaining ring 647 is mounted on exposed side 650 ofOSLM 642. OSLM 642 comprises an Al₂O₃:C material. Inner filter 644 ismade of aluminum. Outer filter 646 is made of copper. Retaining ring 647is made of stainless steel. The reference filter material disc is a thindisc made of polytetrafluoroethylene.

Comparator OSL sensor 630 includes a disc-shaped pellet of OSLM 652, areference filter material disc (not visible in FIGS. 6 and 7), and acylindrical cup-shaped filter 654. OSLM 652 and the reference materialfilter disc are held in place in filter 654 by a retaining ring 655. Thereference filter material disc is sandwiched between OSLM 652 and filter654. Retaining ring 655 is a spring-type retaining ring and is held inplace in inner filter 644 by compression. When retaining ring 655 iscompressed in filter 654, ends 656 and 657 of retaining ring 655 abuteach other. OSLM 652 has a filtered side (not visible in FIGS. 6 and 7),the side of OSLM 652 filtered by the reference filter material disc andfilter 654. OSLM 652 has an exposed side 658, shown in FIG. 7, whichallows the combined dosage of x-ray and gamma radiation to which OSLM652 has been exposed to be read by an OSL reader. Retaining ring 655 ismounted on exposed side 658 of OSLM 652. OSLM 652 comprises an Al₂O₃:Cmaterial. Filter 654 is made of aluminum. Retaining ring 655 is made ofstainless steel. The reference filter material disc is a thin disc madeof polytetrafluoroethylene.

Neutron-sensitive OSL sensor 626 is identical to reference OSL sensor628, except for the substitution of the polytetrafluoroethylene disc inreference OSL sensor 628 for the high-density polyethylene disc inneutron-sensitive OSL sensor 626. Comparator OSL sensor 630 is identicalto reference OSL sensor 628, except that filter 654 is not mounted in anouter filter. In comparator OSL sensor 630, filter 654 functions as anouter filter.

Neutron-sensitive OSL sensor 626, reference OSL sensor 628 andcomparator OSL sensor 630 are similar to each other in that they havethe same OSLM disc, the same cylindrical cup-shaped inner filter and thesame retaining ring. Neutron-sensitive OSL sensor 626, reference OSLsensor 628 and comparator OSL sensor 630 also each include a disc offilter material sandwiched between the OSLM disc and the inner filter.This similarity in the components making up each of the OSL sensorsmaintains a consistent optical condition of reflection and scattering ofthe stimulation and luminescence light within the sensor.

Mounted in a nearly circular recess 659 in sled top face 604 is a roundRadio Frequency ID (RFID) tag 660. RFID tag 660 is held in place inrecess 659 by a double-sided contact adhesive film manufactured by 3M.RFID tag 660 includes an antenna 661 and a memory chip 662. Sled body602 has two parallel lateral sides 663 and 664, two parallel straightend sides 666 and 668, and two slanted corner sides 670 and 672. Betweenneutron-sensitive OSL sensor 626 and straight end side 666 end is aregion 673. Lateral side 663 includes a rail 674 along the length oflateral side 663 on the bottom half of lateral side 663. Rail 674protrudes from lateral side 663. Lateral side 664 includes a rail 676along the length of lateral side 664 on the bottom half of lateral side664. Rail 676 protrudes from lateral side 664. Lateral side 663 includesa U-shaped detent 678 and a tang 679 near end side 668. Rail 674includes three semicircular positioning notches 680, 682 and 684. Sledbottom face 606 includes a recess 686 including indentations 688, 690,692, 694 and 696. Sled top face 604 includes alphanumeric identificationindicia 698 that match alphanumeric identification indicia 232 on upperhousing 104.

Although a double-sided contact adhesive film is used to hold the RFIDtag in place on the dosimeter sled in embodiment of the presentinvention are described above and shown in FIGS. 6 and 7, the RFID tagmay be held on the dosimeter sled by other means. For example, the RFIDtag may be adhered to the dosimeter sled using a UV cured adhesiveplaced along the outside of the RFID tag.

In one embodiment of the present invention, when OSL sensors 626, 628and 630 are being read in turn by a dosimeter reader, positioningnotches 680, 682 and 684 may be used to properly position each OSLsensor in turn within an OSL reader. Positioning notch 680 may be usedto properly position neutron-sensitive OSL sensor 626 within thedosimeter reader. Positioning notch 682 may be used to properly positionReference OSL sensor 628 within the OSL reader. Positioning notch 684may be used to properly position comparator OSL sensor 630 with thedosimeter reader.

In one embodiment of the present invention, the positioning notches maybe used to align the OSL sensors with the optical path of the OSL readerso that the stimulation light and luminescence light are consistentlyapplied and captured. As the dosimeter sled is moved into the OSLreader, the notches open up a light path for a photo-optic sensor tocomplete an electrical circuit whereby the dosimeter reader controlsystem knows that the OSL sensor is correctly positioned over thephoto-engine of the OSL reader to permit analysis.

FIG. 8 shows reference OSL sensor 628 in a disassembled state with innerfilter 644 removed from outer filter 646. FIG. 9 shows reference OSLsensor 628 in an assembled state with inner filter 644 mounted in outerfilter 646. Not visible in FIGS. 8 and 9 is the disc ofpolytetrafluoroethylene sandwiched between OSLM 642 and inner filter644. Due to glare in the images of FIGS. 8 and 9, retaining ring 647 isnot easily visible in FIGS. 8 and 9.

In FIG. 8, the combination of OSLM 642, the polytetrafluoroethylene disc(not visible in FIG. 8), inner filter 644 and retaining ring 647 alsocorresponds to the assembled state of comparator OSL sensor 630.

FIG. 10 shows dosimeter sled 600 being slid into sled recess 412 oflower housing 106. Rail 674 of dosimeter sled 600 slides in groove 432beneath upper lip 434 of lower housing 106. Rail 676 of dosimeter sled600 slides in groove 436 beneath upper lip 438 of lower housing 106.

FIG. 11 shows dosimeter sled 602 fully slid into sled recess 412 so thatend side 666 of dosimeter sled body 602 abuts end wall 418 of lowerhousing 106 and slanted corner side 670 of dosimeter sled 602 abutscorner wall 420 of lower housing 106, i.e., dosimeter sled 602 has ashape that complementarily fits sled recess 412. In the configurationshown in FIG. 11, dosimeter sled 602 is considered “mounted” in lowerhousing 106. In the configuration shown in FIG. 11, copper filter discs472 and 474 of lower housing 106 are positioned directly belowneutron-sensitive OSL sensor 626 and reference OSL sensor 628,respectively of dosimeter sled 602 and circular recess 146 of loweringhousing 106 is positioned directly below comparator OSL sensor 630 ofdosimeter sled 602.

There is no copper filter disc in circular recess 146, becausecomparator OSL sensor 630 may be used to adjust the dose determined byreference OSL sensor 628 at very low energies of x-rays. Therefore,unlike for neutron-sensitive OSL sensor 626 and reference OSL sensor628, it is undesirable for there to be a filter mounted in lower housingbottom 402 beneath comparator OSL sensor 630.

In an alternative embodiment of the present invention, instead of usingtwo copper filter discs, a rectangular filter plate may be mounted in arectangular plate recess in the sled recess of the lower housing. Aswith the copper filter discs, the filter plate shields are locatedbetween the neutron-sensitive OSL sensor and the reference OSL sensorwhen the dosimeter sled is fully slid into the sled recess. By mountingthe filter plate in a less exposed position in the lower housing, thefilter plate is better protected than the copper filter discs which areexternally exposed on the bottom of the lower housing of the dosimeter.

Lower housing 106, with dosimeter sled 602 slid/mounted therein, may bemounted in upper housing 104 by screwing lower housing 106 into upperhousing 104 using threads 236 of upper housing 104 and screw threads 410of lower housing 106. Lower housing 106 is held in place in upperhousing 104, when orientation line 130 of upper housing 104 is parallelto orientation line 152 of lower housing 106. Upper housing 104 can beseparated from lower housing 106 by grasping loops 122 and 124 andturning upper housing 90° counterclockwise so that upper housing 104 andlower housing are oriented as shown in FIG. 1. In the configurationshown in FIG. 1, orientation line 130 is perpendicular to orientationline 152 and upper housing 104 is in a released position relative tolower housing 106.

FIGS. 12, 13, 14, 15 and 16 show an upper housing 1200 of a radiationdosimeter according to one embodiment of the present invention. FIGS. 12and 14 show upper housing top 1202. FIGS. 13 and 15 show upper housingbottom 1204. Upper housing 1200 includes a circular body 1206 and twogenerally trapezoidal-shaped loops 1212 and 1214 located on respectiveopposite sides 1216 and 1218 of circular body 1206. Loops 1212 and 1214have respective openings 1226 and 1228 through which a strap member (notshown) may be threaded so that the dosimeter may be worn on the wrist ofan individual. Upper housing top 1202 has a circular contoured portion1230 and a flat circular upper surface 1232 and includes a curved arrow1242, a circular alignment symbol 1244 and a shallow rounded rectangularrecess 1246. In one embodiment of the present invention, a label withalphanumeric identification indicia (not shown) may be adhered to upperhousing top 1202 in shallow rounded rectangular recess 1246. In anotherembodiment of the present invention, alphanumeric identification indicia(not shown) may be engraved in shallow rounded rectangular recess 1246.Circular interior wall 1254 of upper housing bottom 1204 includesinterior screw threads 1256. Interior wall 1254 surrounds a circularrecess 1262 with a flat bottom 1264.

FIGS. 17, 18, 19, 20, 21, 22, 23 and 24 show a lower housing 1700according to one embodiment of the present invention. FIGS. 17 and 19show a lower housing top 1702. FIGS. 18 and 20 show a lower housingbottom 1704. Lower housing 1700 includes a circular lower housing base1706, a circular disc-shaped platform 1708 having a circular lowerexterior wall 1710 that has screw threads 1712 spaced around thecircumference thereof. Platform 1708 has a flat upper surface 1714 witha rectangular filter plate recess 1716. A thin rectangular energycompensating filter plate (not shown FIGS. 17, 18, 19, 20, 21, 22, 23and 24) may be mounted in filter plate recess 1716. On top of uppersurface 1714 are two upper structures 1718 and 1720, which haverespective upper surfaces 1722 and 1724. Upper structure 1718 includes acurved exterior rail 1726. Upper structures 1718 and 1720 define a sledrecess 1728 having two opposite lateral sides 1730 and 1732, an end wall1734, a slanted corner wall 1736 and an open end 1738. End wall 1734includes a curved wall portion 1740. Lateral side 1730 includes anindentation 1744. Lateral side 1732 includes an indentation 1746.Lateral side 1730 includes a groove 1752 and an upper lip 1754 that runalong the length of lateral side 1730. Lateral side 1732 includes agroove 1756 and an upper lip 1758 that run along the length of lateralside 1732. Lower housing bottom 1704 has a flat bottom surface 1772, aC-shaped groove 1774, two lozenge-shaped recesses 1776 and 1778, and anetched arrow 1780. Opposite ends 1782 and 1784 of C-shaped groove 1774are separated by a gap 1786. Lozenge-shaped recess 1776 includes a lip1790 and an undercut 1792 at an outside end 1794 of lozenge-shapedrecess 1776. Lozenge-shaped recess 1778 includes a lip 1796 and anundercut 1798 at an outside end 1800 of recess 1778. Filter plate recess1716 is located within sled recess 1728 so that a filter plate (notshown) mounted in filter plate recess 1716 will provide shielding to theneutron-sensitive OSL sensor and the reference OSL sensor of a dosimetersled (not shown FIGS. 17, 18, 19, 20, 21, 22, 23 and 24) slid into sledrecess 1728.

FIGS. 25, 26, 27, 28, 29, 30, 31, 32 and 33 show a dosimeter sled body2502 according to one embodiment of the present invention. FIGS. 25 and27 show a sled body top face 2504 of dosimeter sled body 2502. FIGS. 26and 28 show a sled body bottom face 2506 of dosimeter sled body 2502.Sled body top face 2504 and sled body bottom face 2506 are opposite eachother. Dosimeter sled body 2502 includes three openings 2510, 2512 and2514. Openings 2510, 2512 and 2514 include respective top portions 2518,2520 and 2522 and respective bottom portions 2524, 2526 and 2528.Because top portions 2518 and 2520 are smaller than respective bottomportions 2524 and 2526 of openings 2510 and 2512, circular ledges 2540and 2542 formed within openings 2510 and 2512 by top portions 2518 and2520. Because top portion 2522 is smaller than bottom portion 2528 ofopening 2514, a circular ledge 2544 within openings 2514 is formed bytop portion 2522. A round RFID tag (not shown) may be mounted in anearly circular recess 2556 in sled body top face 2504. Dosimeter sledbody 2502 has two parallel lateral sides 2562 and 2564, a curved endside 2566, a substantially straight end side 2568, and two slantedcorner sides 2570 and 2572. Lateral side 2562 includes a rail 2574 alongthe length of lateral side 2562 on the bottom half of lateral side 2562.Rail 2574 protrudes from lateral side 2562. Rail 2574 has beveled edges2575. Lateral side 2564 includes a rail 2576 along the length of lateralside 2564 on the bottom half of lateral side 2564. Rail 2576 protrudesfrom lateral side 2564. Rail 2576 has beveled edges 2577. Lateral side2562 includes a U-shaped detent 2578 and a tang 2579 near end side 2568.Rail 2574 includes three semicircular positioning notches 2580, 2582 and2584. Sled body bottom face 2506 includes a bottom face recess 2586.Bottom face recess 2586 includes indentations 2588, 2590, 2592, 2594 and2596. Sled top face includes alphanumeric indicia 2598. A FNTD (notshown) may be mounted in bottom face recess 2586. Indentations 2588,2590, 2592, 2594 and 2596 in the bottom face recess 2586 aid in mountingan FNTD in bottom face recess 2586 and removing an FNTD from bottom facerecess 2586.

The beveled edges of the rails of the dosimeter sled provide channelsbetween the rails and the sled recess in the lower housing to allowsmall amounts of dust and dirt to accumulate without impeding the sled'straveling in and out of the sled recess.

FIGS. 34 and 35 show a dosimeter sled 3402 including dosimeter sled body2502. In dosimeter sled 3402, neutron-sensitive OSL sensor 3410,reference OSL sensor 3412 and comparator OSL sensor 3414 are mounted inrespective openings 2510, 2512 and 2514 of dosimeter body 3502 and heldin place by press fitting OSL sensor 3410, reference OSL sensor 3412 andcomparator OSL sensor 3414 into respective openings 2510, 2512 and 2514.Neutron-sensitive OSL sensor 3410, reference OSL sensor 3412 andcomparator OSL sensor 3414 abut respective circular ledges 2540, 2542and 2544. Neutron-sensitive OSL sensor 3410 is the OSL sensor closest tocurved end side 2566

Because OSL sensor 3410 is near curved end side 2566, curved end side2566 is curved to expand a region 3416 between OSL sensor 3410 and endside 2566, in comparison to the narrower region 673 betweenneutron-sensitive OSL sensor 626 and straight end side 666 of dosimetersled 600, to ensure that the circular optical light pipe of the OSLreader (not shown in FIGS. 34 and 35) is fully covered whenneutron-sensitive OSL sensor 3410 is read by the OSL reader. There isenough distance between end side 2568 and OSL sensor 3414 to cover theoptical light pipe of the OSL reader, so it is not as important to makeend side 2568 curved.

Neutron-sensitive OSL sensor 3410 includes a disc-shaped pellet of OSLM3422, a converter material disc 3424, a cylindrical cup-shaped innerfilter 3426 and a cylindrical cup-shaped outer filter 3428. OSLM 3422and converter material disc 3424 are held in place in inner filter 3426by a retaining ring 3430. Converter material disc 3424 is sandwichedbetween OSLM 3422 and inner filter 3426. Retaining ring 3430 is aspring-type retaining ring and is held in place in inner filter 3426 bycompression. Compressed in inner filter 3426, ends 3432 and 3434 ofretaining ring 3430 abut each other. Inner filter 3426 is mounted andheld in outer filter 3428 by press fitting inner filter 3426 into outerfilter 3428. OSLM 3422 has a filtered side 3436, the side of OSLM 3422filtered by converter material disc 3424, inner filter 3426 and outerfilter 3428. Neutron-sensitive OSL sensor 3410 has an exposed side 3438that allows the combined dosage of x-ray, gamma and neutron radiation towhich OSLM 3422 has been exposed to be read by an OSL reader. Retainingring 3430 is mounted on exposed side 3438 of OSLM 3422.

Reference OSL sensor 3412 includes a disc-shaped pellet of OSLM 3442, areference filter material disc 3444, a cylindrical cup-shaped innerfilter 3446 and a cylindrical cup-shaped outer filter 3448. OSLM 3442and reference filter material disc 3444 are held in place in innerfilter 3446 by a retaining ring 3450. Reference filter material disc3444 is sandwiched between OSLM 3442 and inner filter 3446. Retainingring 3450 is a spring-type retaining ring and is held in place in innerfilter 3446 by compression. Compressed in inner filter 3446, ends 3452and 3454 of retaining ring 3450 abut each other. Inner filter 3446 ismounted and held in outer filter 3448 by press fitting inner filter 3446into outer filter 3448. OSLM 3442 has a filtered side 3456, the side ofOSLM 3442 filtered by reference filter material disc 3444, inner filter3446 and outer filter 3448. Reference OSL sensor 3412 has an exposedside 3458 that allows the combined dosage of x-ray and gamma radiationto which OSLM 3442 has been exposed to be read by an OSL reader.Retaining ring 3450 is mounted on exposed side 3458 of OSLM 3442.

Comparator OSL sensor 3414 includes a disc-shaped pellet of OSLM 3462, areference filter material disc 3464 and, a cylindrical cup-shaped filter3466. OSLM 3462 and reference filter material disc 3464 are held inplace in filter 3466 by a retaining ring 3468. Reference filter materialdisc 3464 is sandwiched between OSLM 3462 and filter 3466. Retainingring 3468 is a spring-type retaining ring and is held in place in filter3466 by compression. Compressed in inner filter 3466, ends 3470 and 3472of retaining ring 3468 abut each other. OSLM 3462 has a filtered side3474, the side of OSLM 3462 filtered by reference filter material disc3464 and filter 3466. Comparator OSL sensor 3414 has an exposed side3478, which allows the combined dosage of x-ray and gamma radiation towhich OSLM 3462 has been exposed to be read by an OSL reader. Retainingring 3468 is mounted on exposed side 3478 of OSLM 3462.

Neutron-sensitive OSL sensor 3410 is identical to reference OSL sensor3412, except for the substitution of reference filter material disc 3444of reference OSL sensor 3412 for converter material disc 3424 inneutron-sensitive OSL sensor 3410. Comparator OSL sensor 3414 isidentical to reference OSL sensor 3412, except filter 3466 is notmounted in an outer filter. In comparator OSL sensor 3414, filter 3466functions as an outer filter.

In the dosimeter sled of FIG. 34, the OSLM of one of the OSL sensors hasa converter material coated on the filtered side of the OSLM allowingthe OSLM to function as an OSL sensor that senses gamma radiation andneutron radiation. The OSLM of a second OSL sensor has a filterreference material coated on the filtered side of the OSL that allowsthe OSLM to function as an OSL sensor for gamma radiation.

In one embodiment of the present invention, when dosimeter sled 3402 ispositioned under an OSL reader (not shown in FIGS. 34 and 35),positioning notches 2584, 2582 and 2580 may be used to properlyposition, in turn, OSL sensors 3414, 3412 and 3410 relative to anoptical light pipe of a photo-optical engine (not shown in FIGS. 34 and35) the OSL reader. Positioning notch 2580 may be used to properlyposition neutron-sensitive OSL sensor 3410 over the optical light pipeof the OSL reader. Positioning notch 2582 may be used to properlyposition reference OSL sensor 3412 over the optical light pipe of theOSL reader. Positioning notch 2584 may be used to properly positioncomparator OSL sensor 3414 over the optical light pipe of the OSLreader.

Dosimeter sled 3402 may be slid into and out of sled recess 1728 oflower housing 1700 in a fashion similar to the way that dosimeter sled600 slides into and out of sled recess 412 of lower housing 106. Rail2574 of dosimeter sled 3402 slides in groove 1752 beneath upper lip 1754of lower housing 1700. Rail 2576 of dosimeter sled 3402 slides in groove1756 beneath upper lip 1758 of lower housing 1700. When fully slid intodosimeter sled 3402, curved end side 2566 abuts curved wall portion oflower housing 1700. Etched arrow 1780 of lower housing 1700 indicatesthe direction that a dosimeter sled 3402 may be slid out of lowerhousing 1700.

When dosimeter sled 3402 is slid into lower housing 1700, a thinrectangular energy compensating filter (not shown in FIG. 34) mounted infilter plate recess 1716 shields neutron-sensitive OSL sensor 3410 andreference OSL sensor 3412 from radiation, similar to the way that copperfilter discs 472 and 474 shield neutron-sensitive OSL sensor 3410 andreference OSL sensor 3412, respectively. In one embodiment, the thinrectangular energy compensating filter may be molded into filter platerecess 1716. In one embodiment, the thin rectangular energy compensatingfilter may be made of copper.

Lower housing 1700, with dosimeter sled 3402 fully slid/mounted therein,may be mounted in upper housing 104 by screwing lower housing 106 intoupper housing 1200 using screw threads 1256 of upper housing 1200 andscrew threads 1712 of lower housing 1700. Lower housing 1700 may mountedin upper housing 1200, when line A-A, associated with upper housing1200, in FIG. 14 is parallel to line B-B, associated with lower housing1700, of FIG. 19. Upper housing 1200 may be released from lower housing1700 by grasping loops 1212 and 1214 and turning upper housing 90°counterclockwise, so that A-A is perpendicular to line B-B in whichupper housing 1200 is in a released position relative to lower housing1700.

FIG. 36 shows an upper housing top 3602 of an upper housing 3604 of aradiation dosimeter according to one embodiment of the presentinvention. Upper housing 3604 includes a circular body 3606 and twogenerally trapezoidal-shaped loops 3612 and 3614 located on respectiveopposite sides 3616 and 3618 of circular body 3606. Loops 3612 and 3614have respective openings 3626 and 3628 through which a strap member (notshown) may be threaded so that the dosimeter may be worn on the wrist ofan individual. Upper housing top 3602 has a contoured portion 3630, aflat pentagonal upper surface 3632 and five (5) faceted regions 3634.Upper surface 3632 includes a curved arrow 3642, and a circularalignment symbol 3644. A label with alphanumeric identification indicia(not shown) may be adhered to upper housing top 3602 or alpha-numberidentification indicia may be etched into upper housing top 3602. Upperhousing 3604 includes a circular interior wall (not shown) includinginterior screw threads (not shown). Upper housing 3604 may be used witha lower housing of the present invention in a fashion similar to the waythat upper housing 104 may be used with lower housing 106 or upperhousing 1200 may be used with lower housing 1700.

FIG. 37 shows an upper housing top 3702 of an upper housing 3704 of aradiation dosimeter according to one embodiment of the presentinvention. Upper housing 3704 includes a circular body 3706 and twogenerally trapezoidal-shaped loops 3712 and 3714 located on respectiveopposite sides 3716 and 3718 of circular body 3706. Loops 3712 and 3714have respective openings 3726 and 3728 through which a strap member (notshown) may be threaded so that the dosimeter may be worn on the wrist ofan individual. Upper housing top 3702 has a contoured portion 3730, aflat octagonal upper surface 3732 and eight (8) faceted regions 3734.Upper surface 3732 includes a curved arrow 3742, and a circularalignment symbol 3744. A label with alphanumeric identification indicia(not shown) may be adhered to upper housing top 3702 or alpha-numberidentification indicia may be etched into upper housing top 3702. Upperhousing 3704 includes a circular interior wall (not shown) includinginterior screw threads (not shown). Upper housing 3704 may be used witha lower housing of the present invention in a fashion similar to the waythat upper housing 104 may be used with lower housing 106 or upperhousing 1200 may be used with lower housing 1700.

FIG. 38 shows a radiation dosimeter 3802 according to one embodiment ofthe present invention. Radiation dosimeter 3802 includes an upperhousing 3804, a lower housing 3806 and a dosimeter sled 3808 that slidesinto and out of lower housing 3806. Upper housing 3804 includes twoloops 3812 each having an opening 3814. Upper housing 3804 includesinterior screw thread 3816. Lower housing 3806 includes an externalscrew thread 3818 and a sled recess (not visible in FIG. 38). Arectangular copper filter plate 3820 is mounted in a rectangular platerecess (not shown) of lower housing 3806. A neutron-sensitive OSL sensor3822 is mounted in an opening 3824 of dosimeter sled 3808. A referenceOSL sensor 3826 is mounted in an opening 3828 of dosimeter sled 3808. Acomparator OSL sensor 3830 for reference OSL sensor 3826 is mounted inan opening 3832 of dosimeter sled 3808. A fluorescent nuclear trackdetector (FNTD) 3842 is mounted in a bottom face recess 3844 of a bottomface 3846 of dosimeter sled 3808. Dosimeter sled 3808 includes a rail3848. A bottom face 3850 of lower housing 3806 includes twolozenge-shaped recesses 3852 and a C-shaped recess 3854.

Neutron-sensitive OSL sensor 3822 comprises a cylindrical cup-shapedouter filter 3856, a cylindrical cup-shaped inner filter 3858, aconverter material disc 3860, a conformal disc 3862, an OSLM disc 3864and a retaining ring 3866. Retaining ring 3866 holds OSLM disc 3864,conformal disc 3862 and converter material disc 3860 in inner filter3858. Inner filter 3858 is mounted in outer filter 3856. Outer filter3856 is mounted in opening 3822.

Reference OSL sensor 3826 comprises a cylindrical cup-shaped outerfilter 3870, a cylindrical cup-shaped inner filter 3872, a referencefilter material disc 3874, an OSLM disc 3878 and a retaining ring 3880.Retaining ring 3880 holds OSLM disc 3878 and reference filter materialdisc 3874 in inner filter 3872. Inner filter 3872 is mounted in outerfilter 3870. Outer filter 3870 is mounted in opening 3826.

Comparator OSL sensor 3830 comprises a cylindrical cup-shaped filter3882, a reference filter material disc 3884, an OSLM disc 3886 and aretaining ring 3888. Retaining ring 3888 holds OSLM disc 3886 andreference filter material disc 3884 in filter 3882. Filter 3882 ismounted in opening 3830.

Although the OSLM discs shown in FIG. 38 are colored yellow forillustration purposes, the OSLM discs are actually whitish in color.

Conformal disc 3862, which is made of PE, is thinner and more pliablethan the thicker converter material disc 3860, which is made of HDPE. Inone embodiment of the present invention, converter material disc 3860may be made by punching out converter material disc 3860 from a piece ofHDPE material, which may lead to converter material disc 3860 having aconcave or convex shape. When converter material disc 3860 has such aconcave or convex shape, a small gap is formed between convertermaterial disc 3860 and OSLM 3864. Conformal disc 3862 may be used tofill this gap. The combination of conformal disc 3862 and convertermaterial disc 3860 may be viewed as functioning as a “compositeconverter material disc”. Conformal disc 3862 ensures that there is moreintimate contact between this “composite converter material disc” andOSLM 3864. Outer filters 3856 and 3870 are made of copper. Inner filters3858 and 3872 and filter 3882 are made of aluminum. OSLM discs 3864,3878 and 3886 are made of an Al₂O₃:C material. Retaining rings 3866,3880 and 3888 are made of stainless steel.

FIG. 39 shows a sled body bottom face 3902 of a dosimeter sled body 3904of dosimeter sled 3808. Dosimeter sled body 3904 is similar to dosimetersled body 602. Openings 3824, 3828 and 3832 include respective topportions (not shown) and respective bottom portions 3924, 3926 and 3928.Because the top portions are smaller than respective bottom portions3924, 3926 and 3928 of openings 3824, 3828 and 3832, neutron-sensitiveOSL sensor 3822, reference OSL sensor 3826 and comparator OSL sensor3830 mounted in openings 3824, 3828 and 3832 abut respective circularledges 3940, 3942 and 3944 formed within openings 3824 and 3828 by thetop portions of these openings. A round RFID tag (not shown) may bemounted on the top (not shown) of dosimeter sled body 3904. Dosimetersled body 3904 has two parallel lateral sides 3962 and 3964, twosubstantially straight end sides 3966 and 3968, and two slanted cornersides 3970 and 3972. Lateral side 3962 includes a rail 3848 along thelength of lateral side 3962 on the bottom half of lateral side 3962.Rail 3848 protrudes from lateral side 3962. Lateral side 3964 includes arail 3976 along the length of lateral side 3964 on the bottom half oflateral side 3964. Rail 3976 protrudes from lateral side 3964. Lateralside 3962 includes a U-shaped detent 3978 and a tang 3979 near end side3968. Rail 3848 includes three semicircular positioning notches 3980,3982 and 3984. Sled body bottom face 3902 includes a bottom face recess3844. Bottom face recess 3844 includes indentations 3988, 3990, 3992,3994 and 3996. Indentations 3988, 3990, 3992, 3994 and 3996 in bottomface recess 3844 aid in mounting FNTD 3842 in bottom face recess 3844and in removing FNTD 3842 from the bottom face recess 3844.

A sled top face (not shown) of sled 3808 may include alphanumericindicia (not shown).

FIG. 40 shows dosimeter sled 3808 with FNTD 3842 mounted in bottom facerecess 3844. As can be seen in FIG. 40, FNTD 3842 is punch card-shaped.

In the dosimeter sled of FIGS. 38, 39 and 40, the recess is constructedso that one part of the FNTD is in contact with the sled. Examples ofsuitable fluorescent nuclear track detectors are described in U.S.patent application Ser. No. 12/258,035 to Akselrod, et al., entitled“METHOD OF LUMINESCENT SOLID STATE DOSIMETRY OF MIXED RADIATIONS” filedOct. 24, 2008, the entire contents and disclosure of which areincorporated herein by reference. The recess also has facets where aPTFE reference filter is placed and a LiF or other Li based compound isplaced. That is, there are three, adjacent filtered areas over thesingle FNTD sensor. When the dosimeter sled is made of HDPE, that areasenses neutrons in the form of recoil protons and gamma rays/x-rays. Thearea filtered by the PTFE senses only gamma rays/x-rays. The Li filteredarea senses neutrons using an alternative neutron interaction processwhereby the lithium captures the neutron and splits into an alphaparticle and a tritium or H-3 ion. The alpha particle and tritium ion aswell as the recoil proton from the HDPE create tracks in the FNTD thatonce counted or otherwise quantified can be related to the neutron dose.The FNTD is more sensitive than the OSLM to neutrons but not to gammarays and x-rays. The FNTD may be used as a back-up or secondarydosimeter, because its signal is more robust. However, because the FNTDcannot be read in a compact portable reader, the FNTD may be removedfrom the sled and read in a special reader at another location, such asa laboratory.

FIGS. 41, 42, 43, 44 and 45 show a dosimeter upper housing 4100 of aradiation dosimeter according to one embodiment of the presentinvention. FIGS. 41 and 43 show upper housing top 4102. FIGS. 42 and 44show upper housing bottom 4104. Dosimeter upper housing 4100 includes acircular body 4106 and two generally trapezoidal-shaped loops 4112 and4114 located on respective opposite sides 4116 and 4118 of circular body4106. Loops 4112 and 4114 have respective openings 4126 and 4128 throughwhich a strap member (not shown) may be threaded so that the dosimetermay be worn on the wrist of an individual. Upper housing top 4102 has acircular contoured portion 4130 and a flat circular upper surface 4132and includes a curved arrow 4142, a circular alignment symbol 4144 and ashallow rounded rectangular recess 4146. In one embodiment of thepresent invention, a label with alphanumeric identification indicia (notshown) may be adhered to upper housing top 4102 in a shallow roundedrectangular recess 4146. In another embodiment of the present invention,alphanumeric identification indicia (not shown) may be engraved inshallow rounded rectangular recess 4146. Circular interior wall 4154 ofupper housing bottom 4104 includes interior screw threads 4156, acircumferential gasket 4158 and a protrusion 4160. Interior wall 4154surrounds a circular recess 4162 with a flat bottom 4164.

The gasket may be made of a suitable gasket materials such as rubber,silicone, etc.

In one embodiment of the present invention, in addition to screwthreads, the lower housing and/or upper housing has a raised surfaceconsisting of a gasket material, such as silicone or rubber, so that thetwo housings when screwed together provide a water-tight seal.

FIGS. 46, 47, 48, 49, 50, 51, 52, 53, 54 and 55 show a dosimeter sledbody 4602 according to one embodiment of the present invention. FIGS. 46and 48 show a sled body top face 4604 of dosimeter sled body 4602. FIGS.47 and 49 show a sled body bottom face 4606 of dosimeter sled body 4602.Sled top face 4604 and sled body bottom face 4606 are opposite eachother. Dosimeter sled body 4602 includes three openings 4610, 4612 and4614. Openings 4610, 4612 and 4614 include respective top portions 4618,4620 and 4622 and respective bottom portions 4624, 4626 and 4628.Because top portions 4618 and 4620 are smaller than respective bottomportions 4624 and 4626 of openings 4610 and 4612, circular ledges 4640and 4642 are formed within openings 4610 and 4612 by top portions 4618and 4620. Because top portion 4622 is smaller than bottom portion 4628of opening 4614, a circular ledge 4644 within openings 4614 is formed bytop portion 4622. A round RFID tag (not shown, similar to RFID tag 660)may be mounted in an RFID tag recess 4656 in sled body top face 4604.RFID tag recess 4656 includes a flat outer portion 4657 for receiving aflat circumferential part of an RFID tag including an antenna (notshown) and a curved inner portion 4658 for receiving a protruding memorychip of the RFID tag. RFID tag recess 4656 also includes indentations4659 and 4560 for receiving respective adhesive dots used in mountingthe RFID tag in RFID tag recess 4656. Dosimeter sled body 4602 has twoparallel lateral sides 4662 and 4664, a curved end side 4666, asubstantially straight end side 4668, and two slanted corner sides 4670and 4672. Lateral side 4662 includes a rail 4674 along the length oflateral side 4662 on the bottom half of lateral side 4662. Rail 4674protrudes from lateral side 4662. Rail 4674 has beveled edges 4675.Lateral side 4664 includes a rail 4676 along the length of lateral side4664 on the bottom half of lateral side 4664. Rail 4676 protrudes fromlateral side 4664. Rail 4674 has beveled edges 4677. Lateral side 4662includes a U-shaped detent 4678 and a tang 4679 near end side 4668. Rail4674 includes three semicircular positioning notches 4680, 4682 and4684. Sled body bottom face 4606 includes a bottom face recess 4686.Bottom face recess 4686 includes indentations 4688, 4690, 4692, 4694 and4696.

A FNTD (not shown) may be mounted in bottom face recess 4686 in and aFNTD holder 4702 that includes a raised bed 4704 and a spring flange4706. Bottom face recess 4686 also includes a retaining lip 4708. Springflange 4706 and retaining lip 4708 are used to retain an FNTD in FNTDholder 4702. Spring flange 4706 may be pushed outwardly to allow theFNTD to be placed in FNTD holder 4702. Spring flange 4706 then springsback to force the FNTD against a wall 4710 of bottom face recess 4686below retaining lip 4708. Indentations 4688, 4690, 4692, 4694 and 4696in the bottom face recess of the sled body aid in mounting an FNTD inbottom face recess 4686 and in removing an FNTD from bottom face recess4686. Sled top face 4604 includes alphanumeric indicia 4712.

The beveled edges of the rails of the dosimeter sled provide channelsbetween the rails and the sled recess in the lower housing to allowsmall amounts of dust and dirt to accumulate without impeding the sled'straveling into and out of the sled recess.

Because an OSL sensor mounted in opening 4610 would be the closest OSLsensor to curved end side 4666, curved end side 4666 is curved to expanda region 4714 between opening 4610 and curved end side 4666, incomparison to the narrower region 673 between neutron-sensitive OSLsensor 626 and straight end side 666 of dosimeter sled 600, to ensurethat the circular optical light pipe of the OSL reader (not shown inFIGS. 34 and 35) is fully covered when the OSL sensor mounted in opening4610 is read by the OSL reader. There is enough distance between endside 4668 and opening 4614 to cover the optical light pipe of the OSLreader, so it is not as important to make end side 4668 curved.

For the FNTD, there are three (3) filter materials. In the embodiment ofthe present invention shown in FIGS. 46, 47, 48, 49, 50, 51, 52, 53, 54and 55, one filter material is the raised bed of the FNTD holder that ispart of the dosimeter sled made of HDPE and, therefore, acts as neutronconverter. A second filter material is made of PTFE and is placed in thebottom face recess and acts as a reference filter material. A thirdfilter material is a lithium fluoride crystal that converts low energyneutrons into recoil alpha particles and tritium particles.

FIG. 55 shows a dosimeter lower housing 5502 screwed into dosimeterupper housing 4100. Lower housing 4402 is similar to lower housing 1700.Exterior screw threads 5512 of lower housing 5502 engage interior screwthreads 4156 of upper housing 4100. Gasket 4158 provides a seal betweena sealing shelf 5522 of upper housing 4100 and a sealing shelf 5524 oflower housing 5502. Dosimeter sled body 4602 is shown slid into lowerhousing 5502 with an RFID tag 5514 mounted in RFID tag recess 4656. FIG.57 shows greater detail of how gasket 4158 provides a seal between asealing shelf 5522 of upper housing 4100 and a sealing shelf 5524 oflower housing 5502. As shown in FIG. 57, gasket 4158 iscircumferentially mounted in a circular groove 5702 in sealing shelf5522.

FIGS. 58, 59, 60, 61, 62 and 63 show an OSL sensor 5802 and thecomponent parts of OSL sensor 5802 according to one embodiment of thepresent invention. OSL sensor 5802 includes a disc-shaped pellet of OSLM5810, a filter material disc 5812, a cylindrical cup-shaped inner filter5814 and a cylindrical cup-shaped outer filter 5816. OSLM 5810 andfilter material disc 5812 are held in place in inner filter 5814 by aretaining ring 5818. Filter material disc 5812 is sandwiched betweenOSLM 5810 and inner filter 5814. Retaining ring 5818 is a spring-typeretaining ring and is held in place in inner filter 5814 by compression.Compressed in inner filter 5814, ends 5820 and 5822 of retaining ring5818 abut each other. Inner filter 5814 is mounted and held in outerfilter 5816 by press fitting inner filter 5814 into outer filter 5816.OSLM 5810 has a filtered side 5836, the side of OSLM 5810 filtered byfilter material disc 5812, inner filter 5814 and outer filter 5816. OSLM5810 has an exposed side 5840. Retaining ring 5818 is mounted on exposedside 5840 of OSLM 5810.

OSL sensor 5802 has a width/diameter 5842 and a height 5844. OSLM 5810has a width/diameter 5852 and a height 5854.

For the OSL sensor of FIGS. 58 and 59, if the outer filter is made ofcopper, the inner filter is made of aluminum, the OSLM comprises anAl₂O₃:C material and the filter material disc is made of high-densitypolyethylene, then the OSL sensor corresponds to neutron-sensitive OSLsensor 626 of FIGS. 6 and 7. In FIGS. 58 and 59, if the outer filter ismade of copper, the inner filter is made of aluminum, the OSLM comprisesan Al₂O₃:C material and the filter material disc is made ofpolytetrafluoroethylene, then the OSL sensor corresponds to referenceOSL sensor 628 of FIGS. 6 and 7.

For the OSL of FIGS. 58 and 59, if the filter material disc is made of aconverter material, then the OSL sensor corresponds to neutron-sensitiveOSL sensor 3410 of FIGS. 34 and 35. In FIGS. 58 and 59, if the filtermaterial disc is made of a reference filter material, then the OSLsensor corresponds to reference OSL sensor 3412 of FIGS. 34 and 35.

In one embodiment of the present invention, the OSL sensor has awidth/diameter of about 7.7 mm to about 7.8 mm. In one embodiment, theOSL sensor has a width/diameter of about 6.8 mm to about 6.9 mm.

In one embodiment of the present invention, the OSLM has a height ofabout 0.135 mm to about 0.145 mm.

In one embodiment of the present invention, the OSLM has awidth/diameter of about 5.9 mm to about 6 mm.

In one embodiment of the present invention, the OSLM has a height ofabout 0.135 mm to about 0.145 mm.

FIGS. 60 and 61 show OSLM 5810 mounted in inner filter 5814. Innerfilter 5814 includes a circular base 6012 having a cylindrical wall 6014extending therefrom forming a recess 6016 in which OSLM 5810 is mounted.Inner filter 5814 has a width/diameter 6022 and a height 6024. Circularbase 6012 has a thickness 6026. Cylindrical wall 6014 has a thickness6028. Recess 6016 has a width/diameter 6032 that is the same aswidth/diameter 5852 of OSLM 5810.

In one embodiment of the present invention, the inner filter has awidth/diameter of about 6.8 mm to about 6.9 mm. In one embodiment of thepresent invention, the inner filter has a height of about 2.4 mm toabout 2.5 mm. In one embodiment of the present invention, the base ofthe inner filter has a thickness of about 0.2 mm to about 2.1 mm. In oneembodiment of the present invention, the cylindrical wall of the innerfilter has a width of about 0.2 mm to about 0.21 mm. In one embodimentof the present invention, the recess of the inner filter has a minimumwidth/diameter of about 6.1 mm to about 6.2 mm.

FIGS. 62 and 63 shows retaining ring 5818 in a relaxed state having agap 6212 between ends 5820 and 5822. Retaining ring 5818 has a maximumdiameter of 6214, a x-thickness 6216 and a y-thickness 6218. Maximumdiameter 6214 is slightly greater than the width/diameter 6032 of recess6016 of inner filter 5814.

In one embodiment of the present invention, the retaining ring has anx-thickness of about 0.6 mm to about 0.62 mm. In one embodiment of thepresent invention, the retaining ring has an y-thickness of about 0.6 mmto about 0.62 mm.

FIGS. 64 and 65 show outer filter 5816. Outer filter 5816 includes acircular base 6412 having a cylindrical wall 6414 extending therefromforming a recess 6416. Outer filter 5816 has a width/diameter 6422 and aheight 6424. Circular base 6412 has a thickness 6426. Cylindrical wall6414 has a thickness 6428. Recess 6416 has a width/diameter 6432 that issubstantially the same as the width/diameter 6222 of inner filter 5814.

In one embodiment of the present invention, the outer filter has awidth/diameter of about 7.7 mm to about 7.75 mm. In one embodiment ofthe present invention, the outer filter has a height of about 3 mm toabout 3.1 mm. In one embodiment of the present invention, the base ofthe outer filter has a thickness of about 0.36 mm to about 0.37 mm. Inone embodiment of the present invention, the cylindrical wall of theouter filter has a width of about 0.4 mm to about 0.41 mm.

Although cylindrical cup-shaped filters used in the embodiments of theOSL sensors of the present invention are described above and shown inthe drawings, the filters of the present invention may be any of avariety of shapes. An advantage of cylindrical cup-shaped radiationfilters is that they are able to measure a high angle of incidence ofradiation. Instead of having a circular base, the filters of the presentinvention may have bases of other shapes such as oval, triangular,square, rectangular, pentagonal, hexagonal, octagonal, etc. A filter ofthe present invention may be solid, in which case the filter is mountedabove one side of the OSLM or mounted on the OSL. Or, similar to the OSLsensor of FIGS. 58 and 59, the filters may have a recess in which theOSLM may be mounted. The cross-sectional shape of the recess may besimilar to the shape of the base, such as the circular cross-sectionalshape of the recesses of FIGS. 58, 59, 60, 61, 62 and 63.

An OSL sensor of the present invention may include one, two, three orany other number of filters. When the filters are cup-shaped, thefilters may nest, one within each other, as shown in FIGS. 7, 34, 35,58, 59, 60 and 61. Although cup-shaped filters having circularcross-sections are shown in FIGS. 7, 34, 35, 58, 59, 60, 61, 62 and 63,cup-shaped filters having other cross-sectional shapes such as oval,triangular, square, rectangular, pentagonal, hexagonal, octagonal, etc.may also be nested in each other.

In one embodiment of the present invention, an OSL sensor may use onlyone cylindrical cup-shaped filter for the neutron-sensitive OSL sensorand the reference OSL sensor as long as both OSL sensors respondsimilarly to gamma radiation and x-ray radiation.

Although disc-shaped pellets of OSLM used in the embodiments of the OSLsensors of the present invention are described above and shown in thedrawings, the OSLM used in the OSL sensors may have a variety of shapesand cross-sections. When mounted in a filter, the OSLM may have a shapethat is complementary to the shape of the filter, such as a disc-shapedpellet of OSLM mounted in a cylindrical cup-shaped filter or a cube orrectangular box-shaped pellet of OSLM mounted in a filter with arectangular box-shaped recess.

In one embodiment of the present invention, the OSLM may be poured intoa cup-shaped filter in a liquid form. When the OSLM solidifies, the OSLMtakes on the shape of the recess in the cup-shaped filter.

In one embodiment, the OSLM of the present invention may be adisc-shaped pellet comprising Al₂O₃:C made from particles having a grainsize of 30-40 μm. The thickness of the pellet may vary depending on theparticular application.

Although the filters of the present invention in the embodimentsdescribed above and shown in the drawing figures are made of copper andaluminum, the filters of the present invention may be made of othermaterials that are sensitive to radiation. In one embodiment, thefilters may be made of plastic having dispersed therein metal particlesor a metal powder. The type of metal used in such a plastic/metal filterand the size of the particles may vary depending on the function of thefilter. For example, metals having a large atomic weight may bedesirable if the filter is used to remove the presence of low energyx-rays. The degree of x-ray absorption can be adjusted by changing theconcentration and grain size of the metal particles in the plastic/metalfilter. Metals having smaller atomic weights may be used in filtersdesigned to provide less energy compensation. The degree of x-rayabsorption can be adjusted by changing the concentration and grain sizeof the metal particles in the plastic/metal filter.

In one embodiment of the present invention the filters carried by adosimeter sled may include plastic/metal filters each having differenttypes of metal particles and/or having different concentrations of metalparticles and/or having metal particles of different grain sizesdispersed in the plastic material of each filter.

Although in the embodiments shown there are three OSL sensors in thedosimeter sled, in some embodiments of the present invention there maybe one, two, or four or more OSL sensors in the dosimeter sled. Ifnecessary, four or more sensors may be accommodated in the dosimetersled by making each of the OSL sensors smaller or making the dosimetersled longer, thicker or wider.

If necessary, additional sensors and additional types of radiationsensors may be accommodated in the dosimeter sled by making each of theOSL sensors smaller or making the dosimeter sled longer, thicker orwider.

In one embodiment of the present invention, a converter material dischas a thickness of 1 mm to about 1.1 mm. In one embodiment of thepresent invention, the converter material may be a film or sheet havinga thickness of 0.1 mm to about 0.2 mm. In one embodiment the convertermaterial may be a film of polyethylene having a thickness of less than 1mm.

In one embodiment the present invention, a reference filter materialcoating has a thickness of 1 mm to about 1.1 mm. In one embodiment ofthe present invention, the reference filter material may be a film orsheet having a thickness of 0.1 mm to about 0.2 mm. In one embodiment ofthe present invention, the reference filter material may be a film ofpolytetrafluorethylene having a thickness of less than 1 μm.

In various embodiments of the present invention, including theembodiments shown above and described in the drawings, the radiationdosimeter may include an RFID tag that identifies the radiationdosimeter and the individual associated with the radiation dosimeteri.e. the individual who has been wearing the radiation dosimeter. Theidentification information from the RFID tag allows an RFID tag readerthat is part of a dosimeter reader to access information about theradiation dosimeter and the individual from a database. Such informationmay include: the identity of the individual who has been wearing theradiation dosimeter, the last time the radiation dosimeter was read, theserial number of the reader used for the last dosage measurement, arecord of the results of previous readings of the dosimeter, a record ofthe individual's cumulative exposure to various types of radiation, analphanumeric serial number assigned to the dosimeter, an alphanumericserial number assigned to the upper housing, an alphanumeric serialnumber assigned to the lower housing, an alphanumeric serial numberassigned to the dosimeter sled, etc. In some embodiments, the dosimeterreader may also transmit information to the database to update theinformation for the radiation dosimeter and the individual in thedatabase. The database may be stored in the dosimeter reader or storedat another location such as a personal computer, a networked computer, acentralized record database, etc.

Although the identification indicia/alphanumeric serial number assignedto the dosimeter sled and upper housing are identical in the embodimentsdescribed above and shown in the drawings, in other embodiments thedosimeter sled and lower housing may be assigned different alphanumericserial numbers. The dosimeter as a whole and the upper housing may alsobe assigned alphanumeric serial numbers that are the same as ordifferent from the serial numbers assigned to the lower housing anddosimeter sled.

FIG. 66 shows a radiation dosimeter 6602 according to one embodiment ofthe present invention including a strap member 6604 threaded throughopenings 6612 and 6614 of respective loops 6616 and 6618 of radiationdosimeter 6602. Strap member 6604 is threaded beneath the lower housing(not shown) of radiation dosimeter 6602. Strap member 6604 includes abuckle 6632 and loop 6634 through which an end 6636 may be slipped sothat radiation dosimeter 6602 may be worn on an individual's wrist,similar to the way that a wristwatch is worn. Strap member 6604 may beeasily removed from radiation dosimeter 6602 to allow radiationdosimeter 6602 to be read.

FIG. 67 shows a radiation dosimeter 6702 according to one embodiment ofthe present invention including a strap member 6204 threaded throughopenings 6712 and 6714 of respective loops 6716 and 6718 of radiationdosimeter 6702. Strap member 6704 is threaded above upper housing 6722of radiation dosimeter 6702. Strap member 6704 includes a buckle 6732through which an end 6734 may be slipped so that radiation dosimeter6702 may be worn on an individual's wrist, similar to the way that awristwatch is worn. Strap member 6704 may be easily removed fromradiation dosimeter 6702 to allow radiation dosimeter 6702 to be read.

FIG. 68 shows a radiation dosimeter 6802 according to one embodiment ofthe present invention that is attached to a clip 6804. Clip 6804includes a strap member 6812 that is looped through an opening 6820 of aloop 6822 of radiation dosimeter 6802. Strap member 6812 is fastenedback on itself by a snap fastener 6832. Attached to strap member 6812 bya bolt 6834 is a spring clip 6836. Spring clip 6836 may be used to clipradiation dosimeter 6802 to a shirt or pants pocket, a shirt lapel, anecklace worn by an individual, etc. Strap member 6812 may be easilyremoved from radiation dosimeter 6802 to allow radiation dosimeter 6802to be read.

Although in the embodiment shown, the strap member is a one-piece strapmember, in other embodiments of the present invention, the strap membermay be a two-piece strap member.

Various types of strap members, both adjustable and non-adjustable, maybe used with the dosimeter of the present invention. For example, thestrap member may be a one-piece elastic strap. The strap member may alsobe an adjustable strap where the two ends of the strap are buckledtogether in a fashion similar to the way that a belt is buckled aroundan individual's waist or a wristwatch is buckled around an individual'swrist. In such a configuration, one end of the strap member includes abuckle through which the second end of the strap member is inserted. Thestrap member may also be an adjustable strap member in which one end ofthe strap member includes a buckle through which the second end of thestrap is threaded, thereby allowing the length of the strap member to beadjusted by sliding the second strap through the buckle, similar to theadjustable two-piece straps used in backpacks, shoulder bags, fannypacks, etc. An example of such a two-piece strap member is described inU.S. Pat. No. 5,632,429 to Cantwell, the entire contents and disclosureof which are incorporated herein by reference. The strap member may alsobe an adjustable strap member whose ends are adjustably fastenedtogether using hook-and-loop fasteners (e.g. Velcro®) with a strip ofhooks on one end of the strap member and a strip of loops on the otherend of the strap member. Using hook-and-loop fasteners to fasten thestrap member together also allows the size of the strap member to beadjusted by making the strip of hooks and/or the strip of loops longenough that the strips may be fastened together to form a strip memberof various lengths. Various other types of adjustable and non-adjustablestrip members may also be used with the dosimeter of the presentinvention.

The dosimeter of the present invention may be worn by an individual in avariety of ways. For example, the dosimeter may be worn on a straparound a user's wrist, arm, shoulder, head, waist, ankle, leg, etc. Thedosimeter may also be worn on a strap around an article of theindividual's clothing such as a helmet, shirtsleeve, pants leg, etc. Thedosimeter may also be carried in an individual's shirt pocket, pantspocket, etc.

FIGS. 69, 70 and 71 show a portable dosimeter reader 6902 according toone embodiment of the present invention that comprises a dosimeterreader body 6904 mounted in a clamshell type dosimeter reader case 6906.Dosimeter reader body 6904 includes a dosimeter reader chassis 6908, adosimeter drawer 6910, a battery compartment 6912, a display 6920 andcontrol buttons 6922, 6924 and 6926. Control buttons 6922, 6924 and 6926may be used by an individual to: turn on and off the power for dosimeterreader 6902, initiate an analytical sequence for dosimeter reader 6902,and turn on a back light for display 6920 for viewing the results in lowlight. Control buttons 6922, 6924 and 6926 may also be used cyclethrough various screen displays on display 6920 of: dose results, rawdata, calibration factors and other information used in analyzing theresults from reading a dosimeter (not shown in FIGS. 69, 70 and 71).Dosimeter reader body 6904 has three regions: a dosimeterloading/unloading region 6932, a dosimeter ready region 6934 and adosimeter reading region 6936. A housing cover 6940 covers dosimeterready region 6934 and dosimeter reading region 6936. Contained inbattery compartment 6912 are four (4) AA batteries (not visible in FIGS.69, 70 and 71) that provide power for dosimeter reader 6902. Dosimeterreader case 6906 has an upper shell 6952 and an lower shell 6954 thatare pivotably connected to each other by pivot joints 6956 and 6958.Upper shell 6952 includes latches 6960 and 6962 that engage latchreceiving structures 6964 and 6966 on lower shell 6954 to hold uppershell 6952 and lower shell 6954 together when upper shell 6952 ispivoted to cover lower shell 6954. A handle 6968, which may be used tocarry dosimeter reader 6902, is pivotably mounted on lower shell 6954.

Pivot joint 6956 is comprised of upper pivot structures 6972 and 6974 ofupper shell 6952, lower pivot structures 6976, 6978 and 6980 of lowershell 6954, and a pin (not visible in FIGS. 69, 70 and 71) that extendsthrough pivot structures 6972, 6974, 6976, 6978 and 6980. Pivot joint6958 is comprised of upper pivot structures 6982 and 6984 of upper shell6952, lower pivot structures 6986, 6988 and 6980 of lower shell 6954,and a pin (not visible in FIGS. 69, 69 and 70) that extends throughpivot structures 6982, 6984, 6986, 6988 and 6990. Upper shell 6952includes operating instructions 6992 for dosimeter reader 6902.Dosimeter reader body 6904 is mounted in a clamshell type dosimeterreader case 6906 by screws 6994 being screwed through openings 6996 intothreaded opening 6998 in a frame 7002 mounted in lower shell 6954.

Upper shell 6952 includes a peripheral groove 7012 around a peripheraledge 7014 of upper shell 6952. Lower shell 6954 includes a peripheralridge 7022 around a peripheral edge 7024 of lower shell 6954. Whendosimeter reader case 6906 is closed, peripheral ridge 7022 engagesperipheral groove 7012 to form a seal that makes dosimeter reader case6906 air-tight and water-tight. Lower shell includes a pressure reliefvalve 7032 that allows dosimeter reader case 6906 to be easily openedwhen the atmospheric or altitudinal pressure is different during openingthan when the dosimeter reader case 6906 is closed. If the pressureinside dosimeter reader case 6906 is much less that the outsidepressure, dosimeter reader case 6906 may be hard to open.

FIGS. 72, 73, 74 and 75 show details of dosimeter drawer 6910 anddosimeter loading/unloading region 6932. Dosimeter drawer 6910 includesa drawer base 7202 (a dosimeter receiving surface) and a drawer handle7204. Drawer handle 7204 is part of a hollow drawer housing 7206. A topface 7208 of drawer base 7202 includes a C-shaped ridge 7212. Tworetaining tabs 7218 and 7220 extend through respective openings 7222 and7224 in drawer base 7202. Retaining tab 7218 includes an exterior leg7232 and interior leg 7234. Leg 7232 includes a foot 7236. Retaining tab7220 includes an exterior leg 7242 and interior leg 7244. Leg 7242includes a foot 7246. An exposed kidney-shaped dosimeter loop retainer7256 extends through an opening 7258 in drawer base 7202. A coveredkidney-shaped dosimeter loop retainer 7260 extends through an opening7262 in drawer base 7202 and is covered by drawer housing 7206.Dosimeter loop retainer 7260 is slightly longer than dosimeter loopretainer 7256. Dosimeter loop retainer 7256 includes a receiving slot7264, an end wall 7266, a base 7268 and a spring tab 7270. Dosimeterloop retainer 7260 includes a receiving slot 7272, an end wall 7274, abase 7276 and a spring tab 7278. Drawer housing 7206 includes analignment dot 7282 at a curved edge 7284 of drawer housing 7206. Anotheralignment dot 7286 is located on dosimeter reader chassis 6908 adjacentto drawer base 7202. Also visible in FIGS. 72, 73 and 75 is an entrance7292 into a ready region housing 7294 covered by housing cover 6940. Toone side of entrance 7292 there is a piece of foam cushioning 7296.Drawer base 7202 also includes a loop stop 7298. Drawer base 7202 isslidably mounted an opening 7402 in dosimeter reader chassis 6908.Opening 7402 is located between edges 7404 and 7406. A screw 7412 isused to mount an axis mount (not visible in FIGS. 72, 73, 74 and 75) ona bottom face (not visible in FIGS. 72, 73, 74 and 75) of drawer base7202. Exterior leg 7232 has an exterior leg top 7532, interior leg 7234has an interior leg top 7534, exterior leg 7242 has an exterior leg top7542 and interior leg 7344 has an interior leg top 7544.

In FIG. 76 housing cover 6940 is removed to show a reader housing 7602and RFID tag reader 7604 in dosimeter reading region 6936 that areusually covered by housing cover 6940. RFID tag reader 7604 includes anRF antenna 7606. RF antenna 7606 may be used to communicate with the RFantenna of an RFID tag of a dosimeter sled (not shown) that ispositioned below RFID tag reader 7604.

In FIG. 77 housing cover 6940 is removed to show ready region housing7702 and reader housing 7602 that are normally covered by housing cover6940. Ready region housing 7702 has three walls 7704, 7706 and 7708.RFID tag reader 7604 is removed to show OSL reader 7712. OSL reader 7712includes a sled slider 7714 that travels on rails 7716 and 7718 of sliderail base 7720. Sled slider 7714 is moved back and forth on rails 7716and 7718 by drive mechanism 7722. In FIG. 77 a distal end 7732 of drawerbase 7202 is at entrance 7292 of ready region housing 7294. Readerhousing 7602 includes walls 7742, 7744, 7746 and 7708. Wall 7708 isshared with ready region housing 7702.

FIG. 78 shows drive gear 7802, return wheel 7804 and toothed belt 7806of drive mechanism 7722. Toothed belt 7806 is driven by drive gear 7802and travels around drive gear 7802 and return wheel 7804. Sled slider7714 is mounted on toothed belt 7806 by a carriage 7812.

FIG. 79 shows a sled slider motor 7912 mounted on dosimeter readerchassis 6908. Sled slider motor 7912 includes a rotating drive shaft(not visible in FIG. 79) on which drive gear 7802 (not visible in FIG.79) is mounted. Sled slider motor 7912 drives drive gear 7802 using therotating drive shaft, thereby controlling the motion of sled slider 7714(not visible in FIG. 79). FIG. 79 also shows PCB 8420 of OSL reader 7712mounted underneath dosimeter reader chassis 6908 using screw posts 7922and screws 7924. Only two screw posts 7922 and two screws 7924 arevisible in FIG. 79, but four screw posts 7922 and four screws 7924 areused to mount PCB 8420 to dosimeter reader chassis 6908. PCB 8420 isspaced from dosimeter reader chassis 6908 by screw posts 7922 to allowmotor 7912 to be located between dosimeter reader chassis 6908 and PCB8420. In addition, FIG. 79 shows a USB port 7942 in wall 7744 of readerhousing 7602. USB port 7942 allows dosimeter reader 6902 to communicatewith other electronic devices, such as a computer, a data storagedevice, a printer, a monitor, etc. using a USB cable (not shown) pluggedinto USB port 7942.

Although one way of moving the sled slider is described above and showin the drawings, the motion of the sled slider may be moved in otherways. For example, the sled slide may be moved back and forth using arack and pinion drive system in which a rotatable pinion gear is mountedon the sled slider and the sled slider is moved back and forth byrotating the pinion gear along a toothed rack.

FIGS. 80 and 81 show additional details of OSL reader 7712. Visible inFIGS. 80 and 81 is an optical light pipe 8012 of OSL reader 7712.Alignment marks 8022, 8024, 8026 and 8028 on rail 7716 and alignmentmark 8030 may be used to position sled slider 7714 for variousfunctions. Sled slider 7714 includes a bifurcated tang 8034 thatincludes prongs 8036 and 8038 on either side of rail 7716. Sled slider7714 also includes a pusher end 8040. Between bifurcated tang 8034 andpusher end 8040 is a U-shaped detent 8042. Prior to a dosimeter sled(not shown in FIGS. 80 and 81) being pushed by dosimeter drawer 6910into ready region housing 7294, sled slider 7714 travels through anopening 8052 in wall 7708 so that a respective U-shaped detent and tangof a dosimeter sled, such as U-shaped detent 678 and tang 679 ofdosimeter sled 600, will be pushed to engage bifurcated tang 8034 andU-shaped detent 8042, respectively.

Each OSL sensor is moved to a respective reading position by dosimeterreader 6902 determining the distance that sled slider 7714 has moved thedosimeter sled. The slider motor includes an encoder that counts thenumber of revolutions or steps the drive shaft of the motor makes. Thisinformation may be correlated to a movement distance. Alignment marks8022, 8024, 8026 and 8028 on rail 7716 and alignment mark 8030correspond to a number of steps from a reference point.

In one embodiment of the present invention, the dosimeter reader mayinclude a photo-optic sensor for sensing when each of the OSL sensors ofthe dosimeter sled are aligned with the optical light pipe of thedosimeter reader. The photo-optic sensor may be mounted below one of therails on which the slider slides and may be aligned with an alignmentmark on one of the rails. FIGS. 82 and 83 show how the positioningnotches of a dosimeter sled may be used to align the OSL sensors withthe optical path of an OSL reader so that the stimulation light andluminescence light are consistently applied and captured. FIG. 82 showsa dosimeter sled 8202 having a sled body 8204 and three OSL sensors8212, 8214 and 8214 in a non-reading position. OSL sensor 8212 isaligned with a semicircular positioning notch 8222, OSL sensor 8214 isaligned with a semicircular positioning notch 8224 and OSL sensor 8216is aligned with a semicircular positioning notch 8226. A light path,shown by dashed circle 8232, of the photo-optic sensor is blocked bysled body 8204, indicating an optical light pipe 8234, the position ofwhich is shown by a dashed circle, is not aligned with any of the threeOSL sensors. Sled body 8204 has a curved end side 8242. OSL sensor 8212is the closest OSL sensor to curved end side 8242. Between OSL sensor8212 and curved end side 8242 is a region 8244. FIG. 83 shows a readingposition for OSL sensor 8214. Notch 8224 creates an open space throughwhich the light path, shown by solid circle 8332, of the photo-opticsensor may pass, indicating that optical light pipe 8234, the positionof which is shown by a double dashed circle, is aligned with sensor8212. Notches 8224 and 8226 may be used in a similar way to indicate thereading positions for OSL sensor 8214 and 8216, respectively. Curved endside 8242 ensures that region 8244 between OSL sensor 8212 and curvedend side 8242 is large enough so that optical light pipe 8234 is fullycovered when OSL sensor 8212 is read. As shown in FIGS. 82 and 83,optical light pipe 8012 is about the same diameter as the interiordiameter of each of the OSL sensors.

FIG. 84 shows underside 8402 of dosimeter reader body 6904 including anelevator carriage 8412, control electronics 8414, a photo-optical engineframe 8416, an electronic connector 8418 to battery compartment 6912 anda printed circuit board (PCB) 8420 for OSL reader 7712. A proximalmounting strip 8422 and screws 8424 and 8426 are used to mount drawerhousing 7206 on a bottom face 8428 of drawer base 7202 at a proximal end8430 of drawer base 7202. Screws 8424 and 8426 are screwed into screwposts 8432 and 8434 of proximal mounting strip 8422. Mounting strip 8422and screws 8424 and 8426 are also used to mount a proximal flap 8440 ondrawer base 7202 proximal end 8430 of drawer base 7202. Proximal flap8440 includes edges 8442 and 8444. Slide tracks 8452 and 8454 aremounted on dosimeter reader chassis 6908. One edge (not visible in FIG.84) of drawer base 7202 slides in a slide groove (not visible in FIG.84) in slide track 8452 and a second edge (not visible in FIG. 84) ofdrawer base 7202 slides in a slide groove (not visible in FIG. 84) inslide track 8454, thereby allowing drawer base 7202 to slide when pushedand pulled by drawer handle 7204. Edges 8442 and 8444 of proximal flap8440 also slide in the slide grooves of slide tracks 8452 and 8454,respectively. As can be seen by the bending of proximal flap 8440 isflexible, allowing proximal flap to bend or curl downwardly when forcedagainst dosimeter reader case 6906 by dosimeter drawer 6910 moving fromdosimeter ready region 6934 towards dosimeter loading/unloading region6932. Mounted on slide track 8452 is a proximal spring stop 8456.Mounted on slide track 8454 is a proximal sensor switch 8458. Proximalspring stop 8456 prevents elevator carriage 8412 from moving beyondproximal spring stop 8456 and proximal sensor switch 8458 when elevatorcarriage 8412 moves in the direction from dosimeter ready region 6934 todosimeter loading/unloading region 6932. Proximal sensor switch 8458 ispart of a sensor device 8462 that senses when screw post 8434 contactssensor switch 8458, indicating that drawer housing 7206 is in dosimeterloading/unloading region 6932.

FIG. 85 is a close-up view of PCB 8420 for OSL reader 7712.

FIGS. 86, 87, 88 and 89 show the operation of elevator carriage 8412. InFIGS. 86, 87, 88 and 89, dosimeter reader 6902 is shown upside down sothat motion of elevator carriage 8412 from left to right corresponds toelevator carriage 8412 and dosimeter drawer 3914 moving fromloading/unloading region 6932 toward dosimeter ready region 6934.Elevator carriage 8412 includes a barrel 8614 and a loop retainerelevator 8612. Loop retainer elevator 8612 includes two kidney-shapedposts 8616 and 8618. Post 8616 is part of loop retainer 7256. Post 8618is part of loop retainer 7260. Barrel 8614 includes a pinion gear 8622mounted on barrel top 8624 of barrel 8614. Teeth 8626 of pinion gear8622 extend through an opening 8628 in loop retainer elevator 8612 tomesh with teeth 8632 of a rack 8634. Looking at inner barrel fromunderneath dosimeter reader body 6904, as pinion gear 8622 rotatescounterclockwise, elevator carriage 8412 travels along rack 8634 fromdosimeter loading/unloading region 6932 toward dosimeter ready region6934 until elevator carriage 8412 reaches the position shown in FIG. 86.As elevator carriage 8412 moves towards dosimeter ready region 6934 fromdosimeter loading/unloading region 6932, a tongue (not shown) on aninner side (not shown) of loop retainer elevator 8612 travels in agroove 8642 on an exterior wall 8644 of barrel 8614 and loop retainerelevator 8612 is driven upward, thereby causing loop retainers 7256 and7260 to move upwards i.e. up through respective openings 7258 and 7262in drawer base 7202. FIG. 86 shows elevator carriage 8412 at dosimeterloading/unloading region 6932 with loop retainer elevator 8612 atlowered position. FIG. 87 shows elevator carriage 8412 between dosimeterloading/unloading region 6932 and dosimeter ready region 6934 with loopretainer elevator 8612 at a partially raised position. FIGS. 88 and 89show elevator carriage 8412 moved fully towards dosimeter ready region6934 with loop retainer elevator 8612 at a fully raised position.

FIG. 89 shows rack 8634 and slide track 8452 mounted on chassis edge7404 using screws 8912 and 8914. Slide track 8452 is sandwiched betweenrack 8634 and chassis edge 7404. FIG. 89 also shows a bottom face 8922of loop retainer elevator 8612 a circular opening 8924 in loop retainerelevator through which barrel 8714 extends. Screws 8932 and 8934 areused to mount pinion gear 8622 on barrel 8714. An axis post 8942 extendsthrough an opening 8944 in a circular bearing 8946. A spacer clip 8948ensures that space is maintained between circular bearing 8946 and abase 8952 of axis post 8942 as barrel 8714 and pinion gear 8622 rotatearound post 8942. Axis post 8942 is part of an axis mount (not visiblein FIG. 89) that is mounted in a fixed position on drawer base 7202.

The process shown in FIGS. 86, 87, 88 and 89 may also be reversed. Aselevator carriage 8412 moves from dosimeter ready region 6934 towardsdosimeter loading/unloading region 6932, the tongue on the inner side ofloop retainer elevator 8612 travels in a groove 8642 on an exterior wall8644 of barrel 8614, loop retainer elevator 8612 is driven downward,thereby causing loop retainers 7256 and 7260 to move downward i.e. downthrough respective openings 7258 and 7262 in drawer base 7202.

FIGS. 90 and 91 details of retaining tab 7218, retaining tab 7220,pinion gear 8622 and drawer base 7202. As shown in FIG. 91, retainingtab 7218 has a pin 9012 that extends from a tab base 9014. Retaining tab7218 also has an upper body 9016 that extends from tab base 9014.Exterior leg 7232 and interior leg 7234 extend from tab upper body.Retaining tab 7220 has a pin 9022 that extends from a tab base 9024.Retaining tab 7220 also has an tab upper body 9026 that extends from tabbase 9014. Exterior leg 7242 and interior leg 7244 extend from tab upperbody. Retaining tab 7218 is slidably mounted in curved slot 9032 ofpinion gear 8622 using pin 9012. Retaining tab 7220 is slidably mountedin curved slot 9034 of pinion gear 8622 using pin 9012. Tab bases 9014and 9024 rest on top of respective curved slots 9032 and 9034, so thatexterior leg top 7532, interior leg top 7534, exterior leg top 7542 andinterior leg top 7544 are maintained at the same height above piniongear 8622 as pins 9012 and 9022 travel in curved slots 9032 and 9034,respectively. Curved slot 9032 includes a flat portion 9042 and a curvedportion 9044. Curved slot 9034 includes a flat portion 9046 and a curvedportion 9048. As pinion gear 8622 rotates along rack 8634, retainingtabs 7218 and 7220 are prevented from moving with pinion gear 8622 byopenings 7222 and 7224 in drawer base 7202, respectively, and,therefore, pins 9012 and 9022 travel in respective curved slots 9032 and9034 as pinion gear 8622 rotates along rack 8364.

When elevator carriage 8412 and pinion gear 8622 are in dosimeterloading/unloading region 6932, pins 9012 and 9022 are in flat portion9042 of curved slot 9032 and flat portion 9046 of curved slot 9034,respectively. As pinion gear 8622 rotates along rack 8634 from dosimeterloading/unloading region 6932 to dosimeter ready region 6934, pins 9012and 9022 are forced to move along curved portion 9044 of curved slot9032 and curved portion 9048 of curved slot 9034, respectively. Becausecurved portions 9044 and 9048 are farther apart from each other thanflat portions 9042 and 9046, when pins 9012 and 9022 travel in curvedportions 9044 and 9048, retaining tabs 7218 and 7220 are forced tospread outwardly from each other as shown in FIG. 106 and describedbelow.

FIGS. 90 and 91 also show additional features of pinion gear 8622 anddrawer base 7202. Pinion gear 8622 includes openings 9052 and 9054through which screws 8932 and 8934 (not shown in FIGS. 90 and 91) arescrewed to mount pinion gear 8622 on barrel 8614 of elevator carriage8412. An axis mount 9062 includes axis post 8942 on which pinion gear8622 rotates. Axis mount 9062 is mounted in a recess 9064 in bottom face8428 of drawer base 7202 using screw 7412 (not visible in FIGS. 90 and91). A distal mounting strip 9072 including screw posts 9074 and 9076 ismounted on bottom face 8428 of drawer base 7202 using screws 9078 and9080. Mounted on slide track 8452 is a distal spring stop 9082. Mountedon slide track 8454 is a distal sensor switch 9094. Distal spring stop9082 prevents elevator carriage 8412 from moving beyond distal springstop 9082 and distal sensor switch 9084 when elevator carriage 8412moves in the direction from dosimeter loading/unloading region 6932 todosimeter ready region 6934. Distal sensor switch 9084 is part of asensor device 9088 that senses when screw post 9076 contacts distalsensor switch 9084, indicating that drawer housing 7206 is in dosimeterready region 6934.

Also visible in FIG. 90 is a slide groove 9092 of slide track 8454.Slide track 8452 includes an identical slide groove (not visible in FIG.90). One edge of drawer base 7202 slides in slide groove 9092 and asecond edge of drawer base 7202 slides in the slide groove of slidetrack 8452, thereby allowing drawer base 7202 to slide when pushed andpulled by drawer handle 7204.

In FIG. 90, pinion gear 8622 is separated from barrel 8614 and is shownresting on bottom face 8922 of loop retainer elevator 8612.

FIGS. 92 and 93 show photo-optical engine frame 8416, LED board assemblybase 9208 mounted on a bottom face 9210 of photo-optical engine frame8416 by screws 9212, a photomultiplier tube (PMT) mount plate 9214, aPMT 9216, an LED interconnect PCB assembly 9220 is mounted on a sideface 9222 of photo-optical engine frame 8416 using screws 9224, and afilter panel 9234 mounted on photo-optical engine frame 8416. LEDinterconnect PCB assembly 9220 includes a power jack 9236.

FIGS. 94, 95, 96, 97, 98, 99 and 100 show a photo-optical engine 9402and various components of photo-optical engine 9402 of OSL reader 7712.An optical light pipe assembly 9406 that includes optical light pipe8012 that extends through an optical light pipe mount 9408 is mounted ona top face 9410 of photo-optical engine frame 8416 using screws 9412 sothat optical light pipe 8012 extends into opening 9414. A slide railbase 7720 is mounted on optical light pipe mount 9408 using screws 9416.A photodiode printed circuit board (PCB) assembly 9418 including aphotodiode 9420 is mounted on a side face 9422 of photo-optical engineframe 8416 using screws 9424 so that photodiode 9420 extends intoopening 9426. An LED board assembly 9428 including LED board assemblybase 9208 is mounted on bottom face 9210 of photo-optical engine frame8416 using screws 9212. A photomultiplier tube (PMT) lens 9430, a PMTlens gasket 9432 and a blue glass filter 9434 are mounted in an opening9436 in a side face 9438 of photo-optical engine frame 8416. PMT mountplate 9214 is mounted on PMT 9216 using screws 9440. PMT mount plate9214 and PMT mount plate gasket 9442 are mounted on side face 9438 ofphoto-optical engine frame 8416 using screws 9444. LED interconnect PCBassembly 9220 mounted on a side face 9222 of photo-optical engine frame8416 using screws 9224. PMT mount plate includes an opening 9446 and PMTmount plate gasket 9442 includes an opening 9448 that is aligned with(PMT) lens 9430 and blue glass filter 9434. PMT 9216 includesphotocathode 9450.

An OSL filter optic assembly 9452 includes an assembly mount bottom9454, an open circle-shaped lower gasket 9456, a green glass filter9458, an open circle-shaped middle gasket 9460, a dichroic mirror 9462aligned with green glass filter 9458, an open circle-shaped upper gasket9464 and an assembly mount top 9466. Assembly mount top 9466 fits overassembly mount bottom 9454, and together assembly mount top 9466 andassembly mount bottom 9454 enclose the remaining components of OSLfilter optic assembly 9452: lower gasket 9456, green glass filter 9458,middle gasket 9460, dichroic mirror 9462 and upper gasket 9464. When OSLfilter optic assembly 9452 is mounted in an opening 9468 in a side face9470 of photo-optical engine frame 8416. Mounted in an opening 9468,assembly mount top 9466 and assembly mount bottom 9454 are held togetherby a lozenge-shaped interior wall 9472 of opening 9468, thereby holdingtogether the remaining components of OSL filter optic assembly 9452 sothat: lower gasket 9456 is sandwiched between assembly mount bottom 9454and green glass filter 9458, middle gasket 9460 is sandwiched betweengreen glass filter 9458 and a dichroic mirror 9462 and upper gasket 9464is sandwiched between dichroic mirror 9462 and assembly mount top 9466.When held together, OSL filter optic assembly 9452 has a shape thatcomplentarily engages interior wall of 9472 of opening 9468. Assemblymount bottom 9454 has a circular opening 9474 and assembly mount top9404 has a circular opening 9478 that allows light to travel through OSLfilter optic assembly 9416. Assembly mount top 9466 has two curved ends9482 and 9484. OSL filter optic assembly 9452 in held in place inopening 9468 by filter panel 9234 and filter panel gasket 9488 that aremounted on side face 9470 of photo-optical engine frame 8416 usingscrews 9490.

The various gaskets of the present invention may be made of a resilientmaterial such as rubber or plastic. Each gasket shown in FIGS. 94 and 95used in connection with a filter, lens or mirror includes an openingtherein through which light may pass.

LED board assembly 9428 includes a LED (not shown) that transmits thestimulation light used in photo-optical engine 9402.

Photodiode PCB assembly 9418 includes photodiode 9420 that functions asan activity sensor. Photodiode PCB assembly 9418 includes a femaleelectrical connector 9492 for connecting with a male power jack (notshown) to provide photodiode PCB assembly 9418 with power.

As shown in FIGS. 97, 98 and 99, LED interconnect PCB assembly 9220includes a PCB 9722 that is electrically connected by an electricalconnection 9724 to LED board assembly 9428. LED interconnect PCBassembly 9220 includes a power jack 9236 to provide LED 10242 of LEDboard assembly 9428 with power. LED interconnect PCB assembly 9220includes an assembly body 9732, having an opening 9734 in which powerjack 9236 is mounted. Assembly body 9732 includes a complementary recess9736 in which PCB 9722 is mounted and openings 9738 for receiving screws9224.

The OSL filter optic assembly of FIGS. 94, 95, 96, 97, 100 and 101 ismore compact than many previous filter optic assemblies for OSL readersand less subject to becoming misaligned by motion or vibrations, becausethe OSL filter optic assembly is also mounted in an opening so that theOSL filter optic assembly does not substantially move or vibrate whenthe photo-optical engine is moved or vibrated.

Although a particular type of optical filter is described above as beingused in the filter optical assembly, optical filters filtering a varietyof different colors may be used in the optical filter assembly of thepresent invention depending on the wavelength used as a light source forthe stimulation light and the wavelength at which the OSLM of the OSLsensor absorbs light. Also, although a particular type of optical filteris described above as being used as a filter for the emitted lightdetector detecting emitted light from the OSL sensor, optical filtersfiltering a variety of different colors may be used with the emittedlight detector of the present invention depending on the wavelength atwhich OSLM of the OSL luminesces.

FIG. 100 shows photo-optical engine 9402 in an assembled configurationwith a portion 10012 broken away to show a cross-sectional view of OSLfilter optic assembly 9452. A circled region 10014 of portion 10012 ofFIG. 100 is shown in greater detail in FIG. 101. FIG. 101 provides across-sectional view of OSL filter optic assembly 9452 showing: lowergasket 9456 sandwiched between assembly mount bottom 9454 and greenglass filter 9458, middle gasket 9460 sandwiched between green glassfilter 9458 and dichroic mirror 9462 and upper gasket 9464 sandwichedbetween dichroic mirror 9462 and assembly mount top 9466.

The alignment of lenses, mirrors and filters of the photo-optical engineof FIGS. 94, 95, 96, 97, 98, 99, 100 and 101 is also not significantlyaffected by vibrations when a dosimeter reader including photo-opticalengine is moved, because all the components of the photo-optical engineare fixed in place on or in the photo-optical engine frame. Thesecomponents include: the OSL filter optic assembly, the optical lightpipe assembly, the blue glass filter, PMT, activity sensor, LED boardassembly, etc. In one embodiment of the present invention, an OSL readeremploying the photo-optical engine of FIGS. 94, 95, 96, 97, 98, 99, 100and 101 may even be used to read an OSL while the OSL reader is beingmoved. The lens, mirrors and filters of the photo-optical engine areless subject to misalignments caused by vibrations than the lenses,mirrors and filters of other OSL readers because the small distancesbetween components maximize the solid angles through which the variouslight beams must pass for correct transmission through the opticalpathway. The close arrangement of the components minimizes losses due todispersion

In one embodiment of the present invention, four (4) AA batteriesprovide all the power required for operating the dosimeter readerincluding the power to operate: the OSL reader, the engine that drivesthe drive gear that controls the motion of the sled slider, theelectronic controls of the dosimeter reader, the electronic sensors ofdosimeter reader, the display of the dosimeter reader, and thecommunications port for interfacing with external databases. Batterylife depends on the number of analyses performed, the stimulationprotocol employed and the time between analyses in which the reader isidle but still powered. Typically, more than 250 analyses can beperformed for one set of four AA batteries. In one embodiment of thepresent invention, other types of chargeable and non-chargeablebatteries may be used as a power supply for the dosimeter reader. Forexample, one or more alkaline batteries, one or more lithium batteries,etc. may be used as a power supply for the dosimeter reader. In oneembodiment, the total weight of the one or more batteries is less thanabout 100 g.

In one embodiment of the present invention, the dosimeter readerrequires a current of about 90 mA or less for about 1 second to read anOSL sensor. In one embodiment of the present invention, the dosimeterreader requires 80 mA or less of current when the dosimeter reader ispowered and in an idle state and ready to read a radiation dosimeter. Inone embodiment, when the dosimeter reader is turned on, the current inthe dosimeter reader may be 235 mA or less for less than 10 seconds.

In one embodiment of the present invention, the dosimeter reader, withthe dosimeter case in a closed configuration, has a maximum depth ofabout 19 cm or less, a maximum width of about 23.5 cm or less and amaximum height of about 11 cm or less. In one embodiment, the dosimeterreader, with the dosimeter case in a closed configuration has a totalvolume of about 3,065 cm³ or less.

In one embodiment of the present invention, the dosimeter reader,including the dosimeter reader case, has a weight of less than about2,600 g, excluding the weight of the one or more batteries that powerthe dosimeter reader, thereby allowing the dosimeter reader to becarried by a single individual. In one embodiment of the presentinvention, the dosimeter reader, including the dosimeter reader case, ofthe present invention has a weight of less than about 2,700 includingthe weight of the one or more batteries that power the dosimeter reader,thereby allowing the dosimeter reader to be carried by a singleindividual.

FIG. 102 shows OSL reader 7712 and RFID tag reader 7604 of dosimeterreader 6902 in operation reading a dosimeter sled 10204. For simplicityof illustration with respect to OSL reader 7712, only photo-opticalengine 9402 of OSL reader 7712 are shown and other components of OSLreader 7712, such as sled slider 7714, are omitted from FIG. 102.Dosimeter sled 10204 includes three OSL sensors: OSL sensor 10212, OSLsensor 10214 and OSL sensor 10216 and an RFID tag 10218. OSL sensors10212, 10214 and 10216 include an OSLM (not shown) comprising an Al₂O₃:Cmaterial. Dosimeter sled 10204 is pulled out of a radiation dosimeter(not shown) by sled slider 7714 in the direction shown by arrow 10222 sothat OSL sensor 10212, OSL sensor 10214 and OSL sensor 10216 are each inturn read by OSL reader 7712 at a reading position 10226. FIG. 102 showsOSL sensor 10212 in the process of being read.

OSL reader 7712 includes an LED 10242 that is part of LED board assembly9428. LED 10232 is a source of transmitted green stimulation light 10234having a wavelength of about 520 nm. Green stimulation light 10234 isconcentrated by a concentrator 10236 that is part of LED board assembly9428 and then passes through green glass filter 9458 and dichroic mirror9462 aligned with green glass filter 9458. Green glass filter 9458filters out non-green light from green stimulation light 10234, i.e.,green glass filter 9458 is a green filter that passes green light. Greenstimulation light 10234 is then channeled by optical light pipe 8012 sothat an OSL sensor at reading position 10226, OSL sensor 10212 in FIG.102, is exposed to green stimulation light 10234, causing the OSLMmaterial in OSL sensor 10212 to luminesce and emit blue emitted light10246 with a wavelength of about 420 nm. Blue emitted light 10246 isreflected by dichroic mirror 9462, passes through a blue glass filter9434 that filters out non-blue light from blue light in blue emittedlight 10246, i.e., blue glass filter 9434 is a blue filter that passesblue light. Blue glass filter 9434 also filters out any stray light orgreen stimulation light 10234 that is not removed by green glass filter9458. Blue emitted light 10246 is then detected and measured byphotocathode 9450 of photomultiplier tube (PMT) 9216. PMT 9216,operating in a photon counting mode, quantifies the luminescence createdin the OSL sensor based on the detected blue emitted light 10246. Aportion of transmitted green stimulation light 10234 is reflected backby dichroic mirror 9462 through green glass filter 9458 so that greenreflected light 10272 is detected by activity sensor/photodiode 9420.

Green stimulation light 10234 in FIG. 102 defines a light path from LED10242 to OSL sensor 10212. Blue emitted light 10246 defines a light pathfrom OSL sensor 10212 to photocathode 9450. Stimulation light 10234exits optical light pipe 8012 at an exit 10282 and travels a distance10284 from exit 10282 to OSL sensor 10212.

Before, during or after OSL sensor 10212 is read, RFID tag reader 7604reads RFID tag 5418 to retrieve identification information stored in theRFID tag as shown by arrow 10224. This information may be displayed ondisplay 6920 (not shown in FIG. 102) or on a separate display in datacommunication with the dosimeter reader 6902. After OSL sensor 10212,OSL sensor 10214 and OSL sensor 10216 are read by OSL reader 7712, RFIDtag reader 7604 updates RFID tag 10218 with information based on thereadings of OSL sensor 10212, OSL sensor 10214 and OSL sensor 10216.RFID tag reader 7604 may also transmit updated information as each OSLsensor of the three OSL sensors is read. After OSL sensor 10212, OSLsensor 10214 and OSL sensor 10216 have been read, sled slider 7714pushes dosimeter sled 10204 in the direction of arrow 10230 and backinto the radiation dosimeter.

A database 10292 may optionally be in communication with dosimeterreader 6902 or be a part of dosimeter reader 6902. Information about theradiation dosimeter and/or individual wearing the radiation dosimetermay be retrieved from database 10292 as shown by dashed arrow 10294.Updated information about the radiation dosimeter and/or individualwearing the radiation dosimeter may be sent to database 10292 as shownby dashed arrow 10296.

In one embodiment of the present invention, the OSLM in each OSL sensorat the reading position for the OSL sensor is approximately 1 mm fromthe exit of the light guide/optical light pipe.

The activity sensor/photodiode of the photo-optical engine of FIG. 102is designed to determine that the photo-optical engine is functionalwhen a non-zero reading is received by the activity sensor/photodiodedue to stimulated light reflected back to the activitysensor/photodiode.

In one embodiment of the present invention, the emitted light detectorin FIG. 102 is part of a PMT that uses a high sensitivity countingsystem. The amount of blue light emitted during optical stimulation bythe green stimulation light is directly proportional to the radiationdose and the intensity of the green stimulation light. A dosecalculation algorithm is then applied to the measurement to determineexposure results.

The photo-optical engine of FIG. 102 may employ stimulation light havingvarious pulse rates. The photo-optical engine of FIG. 102 may alsoemploy various pulse durations of stimulation light.

Although in FIG. 102 a particular photo-optical engine employingparticular transmitted and detected light wavelengths to determine thedosages of various types of radiation to which a particular type of OSLMis exposed, photo-optical engines transmitting and detecting differentwavelengths may be used with different optically stimulated luminescentmaterials may be employed. The photo-optical engine may also be a pulsedstimulation system.

FIGS. 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114 and 115shown an example of a reading process of the present invention usingradiation dosimeter 102.

FIGS. 103 and 104 show radiation dosimeter 102 placed in a startingposition 10302 in loading/unloading region 6932. An individual placesradiation dosimeter 102 in starting position 10302 so that C-shapedridge 7212 (not visible in FIGS. 103 and 104) engages C-shaped groove454 (not visible in FIGS. 103 and 104) of radiation dosimeter 102.Lozenge-shaped recesses 456 and 458 (not visible in FIGS. 103 and 104)of radiation dosimeter 102 (not visible in FIGS. 103 and 104) fit overretaining tabs 7218 and 7220 (not visible in FIGS. 103 and 104),respectively, of dosimeter reader 6902. Circular alignment symbol 224 ofupper housing 104 is aligned with alignment dot 7282. Curved arrow 222indicates the direction in which upper housing 104 should be rotated torelease upper housing 104 from lower housing 109 (not visible in FIGS.103 and 104).

FIG. 105 shows upper housing 104 of radiation dosimeter 102 rotated sothat radiation dosimeter 102 is in a rotated position 10502 inloading/unloading region 6932. By grasping loops 122 and 124, anindividual rotates upper housing 104 approximately 90° until circularalignment symbol 224 is aligned with alignment dot 7286 so thatradiation dosimeter 102 is in rotated position 10502 where upper housing104 is released from lower housing 106. As upper housing 104 is rotated,loop 122 rotates into and engages receiving slot 7264 of dosimeter loopretainer 7256. Loop 122 is prevented from rotating further by end wall7266 of dosimeter loop retainer 7256 and loop stop 7298. Loop 122 alsoengages spring tab 7270 and rests on base 7268 of loop retainer 7256.Also, as upper housing 104 is rotated, loop 124 rotates into and engagesreceiving slot 7272 of dosimeter loop retainer 7260 (not visible in FIG.105). Loop 124 is prevented from rotating further by end wall 7274 (notvisible in FIG. 105) of dosimeter loop retainer 7260 and loop stop 7298.Loop 122 also engages spring tab 7278 (not visible in FIG. 105) andrests on base 7276 (not visible in FIG. 105) of loop retainer 7260.While upper housing 104 is rotated, lower housing 106 (not visible inFIG. 105) is prevented from rotating by the engagement of C-shaped ridge7212 (not visible in FIG. 105) with C-shaped groove 454 (not visible inFIG. 105) of radiation dosimeter 102 and the engagement oflozenge-shaped recesses 456 and 458 (not visible in FIG. 105) withretaining tabs 7218 and 7220 (not visible in FIG. 105), respectively, ofdosimeter reader 6902. FIG. 105 shows drawer base 7202 in a positionthat corresponds to the position of elevator carriage 8412 shown inFIGS. 88 and 89.

A user pushes drawer handle 7204 of dosimeter drawer 3914 so thatradiation dosimeter 102 is moved by drawer base 7202 into ready regionhousing 7294. As radiation dosimeter 102 is pushed into ready regionhousing 7294, retaining tabs 7218 and 7220 spread outwardly so that foot7236 of exterior leg 7232 retaining tab 7218 and foot 7246 of exteriorleg 7242 of retaining tab 7220 engage undercuts 10602 and 10604 oflozenge-shaped recesses 456 and 458, respectively as shown in FIG. 106.Retaining tabs 7218 and 7220 are spread outwardly from each other due tothe interactions of retaining tabs 7218 and 7220 with openings 7222 and7224 of drawer base 7202 and curved slots 9032 and 9034 of pinion gear8622, as described in greater detail above with respect to FIGS. 90 and91. In the state shown in FIG. 106, foot 7236 captures lip 10612 oflozenge-shaped recess 456, and foot 7246 captures lip 10614 oflozenge-shaped recess 458, thereby allowing retaining tab 7218 andretaining tab 7220 to hold lower housing 106 on drawer base 7202 asupper housing 104 (not shown in FIG. 106) is lifted up from lowerhousing 106 as radiation dosimeter 102 is moved from dosimeterloading/unloading region 6932 to dosimeter ready region 6934. Retainingtabs 7218 and 7220 are spread outwardly by the interaction of retainingtabs 7218 and 7220 with respective curved slots 9032 and 9034 of piniongear 8622 as pinion gear 8622 travels along rack 8634, as describedabove with respect to FIGS. 93 and 94.

Although a particular combination of complementary lower housingrotation preventing engagement structures, i.e. a C-shaped recess on thelower housing engaging a C-shaped ridge on the drawer base, are used inthe embodiment of the present invention shown in FIGS. 103, 104, 105,106, 107, 108, 109, 110, 111, 112, 113, 114 and 115, other combinationsof rotation preventing engagement structures may be used in the presentinvention. For example, the drawer base could includes two or more postsand the lower housing could includes recesses for receiving and engagingthe posts.

Although a particular combination of lower housing retaining structures,i.e. the retaining tabs engaging the lips and undercuts of thelozenge-shaped recesses, are used in the embodiment of the presentinvention shown in FIGS. 103, 104, 105, 106, 107, 108, 109, 110, 111,112, 113, 114 and 115, other combinations of lower housing retainingstructures may be used in the present invention.

FIG. 107 shows radiation dosimeter 102 in rotated position 10502 of FIG.105 from the side. FIG. 108 shows radiation dosimeter 102 is moved bydrawer base 7202 into ready region housing 7294. As shown in FIG. 108,upper housing 104 has been lifted above lower housing 106 by loopretainers 7256 and 7260 being elevated by loop retainer elevator 8612(not visible in FIG. 108) as radiation dosimeter 102 moved by drawerbase 7202 into ready region housing 7294. FIG. 109 shows radiationdosimeter 102 moved further by drawer base 7202 into ready regionhousing 7294 and upper housing 104 being lifted further above lowerhousing 106 by loop retainers 7256 and 7260 being further elevated byloop retainer elevator 8612 (not visible in FIG. 109). Foam cushioning7296 is removed in FIG. 109 to show greater detail of upper housing 104and lower housing 106.

FIGS. 110, 111 and 112 show drawer base 7202 fully pushed into readyregion housing 7294. Housing cover 6940 is shown removed in FIG. 111 toshow radiation dosimeter 102 in a dosimeter ready position 11102 indosimeter ready region 6934 of radiation dosimeter reader 6902. Indosimeter ready position 11102, radiation dosimeter 102 is fullyshielded from light by ready region housing 7294, housing cover 6940 anddrawer housing 7206. Upper housing 104 is fully raised above lowerhousing 104 by loop retainers 7256 and 7260 at dosimeter ready position11102. FIGS. 110, 111 and 112 also show how proximal flap 8440 forms afloor beneath opening 7402.

FIG. 112 shows radiation dosimeter 102 at dosimeter ready position 11102with upper housing 104 removed to show how lower housing 106 anddosimeter sled 600 interact with various components of dosimeter reader6902 at dosimeter ready position 11102. At ready position 11102,bifurcated tang 8034 of sled slider 7714 engages U-shaped detent 678 ofdosimeter sled 600, U-shaped detent 8042 of sled slider 7714 engagestang 679 of dosimeter sled 600, and a pusher end 8040 of slider 7714abuts end side 668 of dosimeter sled 600. The engagement of bifurcatedtang 8034 with U-shaped detent 678 and the engagement of U-shaped detent8042 with tang 679 allows slider 4214 to pull dosimeter sled 600 in alinear direction into reading region 6936. At dosimeter ready position11102, lower housing 106 continues to prevented from rotating byC-shaped ridge 7212 engaging C-shaped groove 454. At dosimeter readyposition 11102, lower housing 106 continues to be held on drawer base7202 by retaining tabs 7218 and 7220 continuing to capture lips 10612and 10614 of lozenge-shaped recesses 456 and 458, respectively.

The position of drawer base 7202 shown in FIGS. 110, 111 and 112corresponds to the position of elevator carriage 8412 shown in FIGS. 88and 89.

FIG. 113 shows dosimeter sled 600 being pulled out of sled recess 412 oflower housing 106 by sled slider 7714 (not visible in FIG. 113) throughopening 8052 in wall 7708 and into dosimeter reading region 6936.

FIG. 114 shows dosimeter sled 600 pulled to a reading position 11402 forcomparator OSL sensor 630 where OSL reader 7712 (not visible in FIG.114) is directly beneath OSL sensor 630 so that exposed side 658 of OSLM652 (not visible in FIG. 114) is exposed to OSL reader 7712. Positioningnotch 684 (not visible in FIG. 114) is aligned with alignment mark 8022and alignment mark 8030. At reading position 11402, RFID tag 660 is alsoread by RFID tag reader 7604 (which is removed in FIG. 114 to showgreater detail inside dosimeter reading region 6936).

FIG. 115 shows dosimeter sled 600 pulled to a reading position 11502 forreference OSL sensor 628, where OSL reader 7712 (not visible in FIG.115) is directly beneath OSL sensor 628 so that exposed side 650 of OSLM642 (not visible in FIG. 115) is exposed to OSL reader 7712. Positioningnotch 682 (not visible in FIG. 115) is aligned with alignment mark 8022and alignment mark 8030. At reading position 11502, an etched alignmentmark 11512 on dosimeter sled 600 for OSL sensor 628 is aligned withalignment mark 8022 and alignment mark 8030. FIG. 115 also shows anetched alignment mark 11514 on dosimeter sled 600 for OSL sensor 626.

After reference OSL sensor 628 is read, slider 7714 pulls dosimeter sled600 to a reading position (not shown) where neutron-sensitive OSL sensor626 is in position to be read above OSL reader 7712. In the readingposition for neutron-sensitive OSL sensor 626, exposed side 640 of OSLM632 is exposed to OSL reader 7712. At the reading position for OSLsensor 626, positioning notch 680 is aligned with alignment mark 8022and alignment mark 8030. Also, at the reading position for OSL sensor626, etched alignment mark 11514 is aligned with alignment mark 8022 andalignment mark 8030.

After comparator OSL sensor 630, reference OSL sensor 628 andneutron-sensitive OSL sensor 626 have each been read by OSL reader 7712,sled slider 7714 pushes dosimeter sled 600 back into sled recess 412 oflower housing 106 in a configuration identical to the one shown in FIGS.110, 111 and 112. By pulling on drawer handle 7204, drawer handle 7204may then be pulled back so that drawer base 7202 is at dosimeterloading/unloading region 6932 in a configuration identical to the oneshown in FIGS. 105 and 107. As drawer base 7202 is moved towardsdosimeter loading/unloading region 6932, dosimeter upper housing 104 islowered by loop retainers 7256 and 7260 being lowered by loop retainerelevator 8612. Also, as radiation dosimeter 102 drawer base 7202 ismoved towards dosimeter loading/unloading region 6932, retaining tabs7218 and 7220 retract inwardly so that foot 7236 of exterior leg 7232retaining tab 7218 and foot 7246 of exterior leg 7242 of retaining tab7220 no longer engage undercuts 10602 and 10604 of lozenge-shapedrecesses 456 and 458, respectively. Once radiation dosimeter 102 hasbeen moved back to dosimeter loading/unloading region 6932, upperhousing 104 may be then screwed onto lower housing 106, by graspingloops by an individual grasping loops 122 and 124 and rotating upperhousing 104 90° in a direction opposite to curved arrow 222 so thatradiation dosimeter 102 is in the configuration shown in FIGS. 103 and104. Radiation dosimeter 102 may then be removed from drawer base 7202.

EXAMPLE EXAMPLE

Dosimeter tests were conducted to determine the responses of three OSLsensors to radiation of different energies.

Groups of five dosimeters each were irradiated to a deep dose (definedas Hp10, or the dose occurring at a depth of 10 mm in tissue) of 500mrem (5 mSv) from gamma or x-rays with mean energies of 53 keV, 73 keV,118 keV, 162 keV and 662 keV. The dosimeters were mounted on acylindrical phantom representing the wrist composed ofpolymethymethacrylate that is 7.3 cm in diameter and 45 cm tall. Afterexposure, the dosimeters were read out using a dosimeter reader of thetype described above and shown in the drawings. FIG. 116 plots the meanluminescence in units of photon counts per mrem of delivered deep dosefor each of the three OSL sensors in the dosimeter. The sensor labeledAl refers to the OSL sensor consisting of a single energy compensatingcup composed of aluminum with a PTFE conversion filter between the OSLMand the aluminum cup. Likewise, the sensor labeled CuT refers to the OSLsensor consisting of an inner energy compensating cup of aluminum and anouter energy compensating cup of copper with a PTFE conversion filterbetween the OSLM and the inner cup of aluminum. The sensor labeled CuPis similar to the CuT sensor except that an HDPE neutron conversionfilter is substituted for the PTFE conversion filter. The Al sensorshows an increasing response to x-rays with energies below 100 keV,demonstrating the energy compensation effect of the copper outer cup.FIG. 117 portrays the same data normalized to the response for the 662keV gamma rays. This demonstrates the energy compensation effect of thefilters to create the same response per unit dose at all energiestested. FIG. 118 portrays the relative response of the Al and CuPsensors to the reference sensor, CuT. This graph demonstrates theequality of the gamma ray and x-ray response between the CuT and CuPsensors so that any response in the CuP that is greater than thatmeasured for the CuT can be attributed to the neutron dose.

While the present invention has been disclosed with references tocertain embodiments, numerous modifications, alterations, and changes tothe described embodiments are possible without departing from the spiritand scope of the present invention, as defined in the appended claims.Accordingly, it is intended that the present invention not be limited tothe described embodiments, but that it has the full scope defined by thelanguage of the following claims, and equivalents thereof.

1. A method comprising the following steps: (a) moving a selectedoptically stimulated luminescence (OSL) sensor of two or more OSLsensors mounted on a dosimeter sled to a reading position for theselected OSL sensor; (b) reading the selected OSL sensor at the readingposition using an OSL reader to measure a radiation dosage to which adosimeter in which the dosimeter sled has been mounted has been exposed;and (c) repeating steps (a) and (b) for each of the two or more OSLsensors, wherein each OSL sensor comprises an optically stimulatedluminescent material (OSLM) mounted in one or more cylindricalcup-shaped energy compensating filters, and wherein the dosimeter sledis part of a dosimeter.
 2. The method of claim 1, wherein the two ormore OSL sensors comprises: a first OSL sensor and a second OSL sensor,wherein a first radiation dosage of neutron, x-ray and gamma rayradiation for the dosimeter is measured from the first OSL sensor andwherein a second radiation dosage of x-ray and gamma ray radiation forthe dosimeter is measured from the second OSL sensor.
 3. The method ofclaim 2, further comprising the following step: (d) determining aneutron radiation dosage to which the dosimeter has been exposed basedon the first radiation dosage and the second radiation dosage.
 4. Themethod of claim 3, further comprising the following step: (e) reading anRFID tag that is part of the dosimeter sled to obtain information thatmay be used in determining the neutron radiation dosage in step (d),wherein the neutron radiation dosage determined in step (d) is based onthe information obtained from the RFID tag in step (e).
 5. The method ofclaim 3, further comprising the following step: (e) determining theamount stimulation light used in conducting step (a), wherein theneutron radiation dosage determined in (d) is based on the amount ofstimulation light determined in step (e).
 6. The method of claim 3,further comprising the following step: (e) determining the amount ofnon-radiation induced light received by the OSL reader conducting step(b) for use in determining the neutron dosage in step (e).
 7. The methodof claim 3, wherein the first OSL sensor comprises a converter materialdisc located between the OSLM of the first OSL and a base of a firstcylindrical cup-shaped filter of the first OSL sensor in which the OSLMof the first OSL sensor is mounted.
 8. The method of claim 7, whereinthe converter material disc comprises high-density polyethylene andwherein there is a conformal disc comprising polyethylene locatedbetween the OSLM and the converter material disc.
 9. The method of claim7, wherein the second OSL sensor comprises a reference filter materialdisc comprising polytetrafluoroethylene located between the OSLM of thesecond OSL sensor and a base of a first cylindrical cup-shaped filter ofthe second OSL sensor in which the OSLM of the second OSL sensor ismounted.
 10. The method of claim 9, wherein the first cylindricalcup-shaped filter for first OSL sensor and the second OSL sensor areeach mounted in a respective second cylindrical cup-shaped filter andwherein the respective first cylindrical cup-shaped filters of the firstOSL sensor and the second OSL sensor are substantially identical to eachother.
 11. The method of claim 3, wherein the two or more sensorscomprise a third OSL sensor, wherein the third OSL sensor is acomparator OSL sensor for the second OSL sensor, wherein a thirdradiation dosage of x-ray and gamma ray radiation for the dosimeter ismeasured from the third OSL sensor, and wherein the method of claim 5further comprises the following step: (e) determining the x-ray andgamma ray radiation dosage to which the dosimeter has been exposed basedon the second radiation dosage and the third radiation dosage.
 12. Themethod of claim 11, further comprising the following step: (f) readingan RFID tag that is part of the dosimeter sled to obtain informationthat may be used in determining the x-ray and gamma ray radiation dosagein step (e), wherein the x-ray and gamma ray radiation dosage determinedin step (e) is based on the information obtained from the RFID tag instep (f).
 13. The method of claim 11, further comprising the followingstep: (f) determining the amount of stimulation light used in conductingstep (a), wherein the x-ray and gamma ray radiation dosage determined in(e) is based on the amount of stimulation light determined in step (f).14. The method of claim 11, further comprising the following step: (f)determining the amount of non-radiation induced light received by theOSL reader conducting step (b) for use in determining the x-ray andgamma ray radiation dosage dosage in step (e).
 15. The method of claim11, wherein the third OSL sensor comprises a reference filter materialdisc comprising polytetrafluoroethylene located between the OSLM of thethird OSL sensor and a base of a first cylindrical cup-shaped filter ofthe third OSL sensor in which the OSLM of the third OSL sensor ismounted.
 16. The method of claim 1, wherein step (b) comprisesstimulating the OSLM of the selected OSL sensor with pulses ofstimulation light of varying duration.
 17. The method of claim 1,wherein step (b) comprising stimulating the OSLM of the selected OSLsensor with pulses of stimulation light of varying frequency.
 18. Themethod of claim 1, further comprising the following steps: (d) measuringa luminescence intensity of the selected OSL sensor; and (e) selecting apulsed optically stimulated luminescence (POSL) process based on theluminescence intensity measured in step (d).
 19. The method of claim 18,wherein step (d) is conducted for less than about 10% of the time thatstep (b) is conducted for each of the two or more OSL sensors.
 20. Themethod of claim 1, wherein the OSLM comprises an Al₂O₃:C material. 21.The method of claim 20, wherein the Al₂O₃:C material has a grain size of30 to 40 μm.
 22. The method of claim 1, wherein each OSL sensor of thetwo or more OSL sensors has an exposed side on a first face of thedosimeter sled and a filtered side on a second face of the dosimetersled.
 23. The method of claim 1, further comprising the following step:(d) pulling out the dosimeter sled from a recess in a housing of thedosimeter in which the dosimeter sled is mounted prior to step (a). 24.A method comprising the following steps: (a) moving an opticallystimulated luminescence (OSL) sensor mounted on a dosimeter sled to areading position for an OSL reader; and (b) reading the OSL sensor atthe reading position using the OSL reader to measure a radiation dosageto which a dosimeter in which the dosimeter sled has been mounted hasbeen exposed, wherein the OSL sensor comprises an optically stimulatedluminescent material (OSLM) mounted in one or more cylindricalcup-shaped energy compensating filters.